The present invention relates to a method for producing a polyoxyalkylene polyol, and a method for producing derivatives thereof such as a polymer-dispersed polyol, isocyanate group-ended prepolymer, polyurethane and the like, by applying the above-described production method. More particularly, the present invention relates to a method for producing a polyoxyalkylene polyol in which a crude polyoxyalkylene polyol obtained by addition polymerization of an epoxide compound to an active hydrogen compound in the presence of a catalyst composed of a compound having a Pxe2x95x90N bond is allowed to contact with a solid acid having specific form, and a method for producing derivatives thereof such as a polymer-dispersed polyol, isocyanate group-ended prepolymer, flexible polyurethane foam, polyurethane resin and the like, by applying the above-described production method.
Usually, a polyoxyalkylene polyol is produced at industrial scale by addition polymerization of an alkylene oxide to an active hydrogen compound in the presence of a potassium hydroxide (hereinafter, referred to as KOH) catalyst. That is, a KOH catalyst and an active hydrogen compound are dehydrated by heating under reduced pressure to prepare a polymerization initiator (potassium salt of an active hydrogen compound), then, the polymerization initiator is reacted with an alkylene oxide being supplied continuously until desired molecular weight is obtained under conditions of a reaction temperature of 105 to 150xc2x0 C. and a maximum reaction pressure of 490 to 588 kPa to give a crude polyoxyalkylene polyol. Then, potassium in the crude polyoxyalkylene polyol is neutralized with an acid such as an inorganic acid and the like, dehydrated a and dried to precipitate a potassium salt which is subjected to a purification process such as filtration and the like, giving a polyoxyalkylene polyol.
However, it is known that, in the case of addition polymerization of propylene oxide which is most widely used as an alkylene oxide, a monool having an unsaturated group at the molecular end is by-produced together with an increase in the molecular weight of a polyoxyalkylene polyol.
Usually, the molecular weight of a monool corresponds to the total unsaturation degree (hereinafter, referred to as Cxe2x95x90C) of a polyoxyalkylene polyol. Since this monool has a lower molecular weight as compared with that of a polyoxyalkylene polyol produced in the main reaction, the monool enlarges significantly the molecular weight distribution of the polyoxyalkylene polyol and reduces the average functionality. Therefore, a polyurethane resin obtained by using a polyoxyalkylene polyol having high monool content gives undesirable results such as an increase in hysteresis, a decrease in hardness, a lowering of curing property, an increase in compression set and the like irrespective of a physical state of the resin, that is, foam or elastomer.
Therefore, there have been conducted various studies to inhibit formation of the by-product monool and to improve productivity of the polyoxyalkylene polyol. For example, U.S. Pat. No. 3,829,505 and U.S. Pat. No. 4,472,560 suggest a method in which a double metal cyanide complex (hereinafter, referred to as DMC) is used as a catalyst for propylene oxide addition polymerization. DMC manifests excellent property as a polymerization catalyst of propylene oxide. However, when DMC is used as a catalyst and ethylene oxide is addition-polymerized as an alkylene oxide, it is necessary to once deactivate DMC by reaction with an oxidizer such as a gas containing oxygen, a peroxide, sulfuric acid and the like, to separate catalyst residue from a polyol, and further to conduct addition polymerization of ethylene oxide using an alkaline metal hydroxide such as KOH, an alkaline metal alkoxide and the like (U.S. Pat. No. 5,235,114), leading to complicated operations.
Japanese Laid-Open Patent Publication (JP-A) No. Hei-7-278289 discloses a polyoxyalkylene polyol having a hydroxyl value (hereinafter, abbreviated as OHV) of 10 to 35 mg KOH/g, a monool maximum content of 15 mol %, and further, a head-to-tail (hereinafter, simply expressed as Hxe2x80x94T) bond minimum selectivity due to propylene oxide addition polymerization of 96% obtained by using cesium hydroxide and the like as a catalyst. This polyoxyalkylene polyol is a polyoxyalkylene polyol which has low viscosity even if the monool content is reduced and gives a flexible polyurethane foam having an excellent mechanical quality, and excellent properties. However, it requires a fairly long reaction time to produce, for example, a polyoxyalkylene polyol of high molecular weight having an OHV of 15 mg KOH/g and a low monool content of 15 mol % or less using cesium hydroxide as a catalyst, therefore, when productivity of the polyol is taken into consideration, this catalyst is not necessarily satisfactory.
On the other hand, as a catalyst for producing a polyoxyalkylene polyol containing no metal, phosphazene compounds have been suggested (EP 0763555, Macromol. Rapid Commun., Vol. 17, pp. 143 to 148, 1996 and Macromol. Symp., Vol. 107, pp. 331 to 340, 1996). When these phosphazene compounds are used as a catalyst for producing a polyoxyalkylene polyol, advantages wherein that productivity of the polyoxyalkylene polyol increases steeply in addition to low by-production ratio of a monool exist.
The present inventors have suggested a polyoxyalkylene polyol in which Cxe2x95x90C content is low, Hxe2x80x94T bond selectivity is high and the molecular weight distribution of a polyol which is a main reaction component is sharp using as a catalyst a novel phosphazenium compound, and a method for producing this polyoxyalkylene polyol in a patent application relating to International Publication WO 98/54241 (EP 0916686A1). When a phosphazenium compound is used as a catalyst for producing a polyoxyalkylene polyol, even if production of a polyol is conducted using propylene oxide as a monomer, there are advantages in that the by-production ratio of a monool is low and the productivity of a polyoxyalkylene polyol increases steeply.
On the other hand, phosphine oxide compounds are publicly a known in addition to phosphazene compounds and phosphazenium compounds (Journal of General Chemistry of the USSR, Vol. 55, p. 1453 (1985)). In this literature, a method for producing a phosphine oxide compound, and a reaction example using methyl iodide are described. However, there is no disclosure regarding use of a phosphine oxide compound as a catalyst for producing a polyol.
The present inventors have suggested a method for purifying a crude polyoxyalkylene polyol produced by using a phosphazenium compound as a catalyst in the above-described patent application relating to International Publication WO 98/54241 (EP 0916686A1) (methods e to h on page 11, line 21 to page 12, line 17). The method e in this purification method is an excellent method for purifying a polyol which can control the catalyst-remaining amount to 150 ppm or less by synergism of an acid, water and adsorbent in specific amounts. The method f is a method in which an organic solvent inactive with a polyol is used together in specific amounts in the method e. In both of the methods e and f, an adsorbent in specific amounts is used. However, in these methods, a remaining catalyst is removed using an adsorbent after neutralization treatment with an acid as pre-treatment, and the process is slightly longer.
In both of the methods g and h which are other methods using no adsorbent, water or an organic solvent in large amounts is used. Therefore, after the purification treatment, there is required a process for removing water or an organic solvent from a polyoxyalkylene polyol. Depending on the molecular structure of a polyoxyalkylene polyol, the yield of a polyol may sometimes decrease since a part of the polyol is dissolved in water due to contact operation with a large amount of water. Any of these methods include a longer process, and is not necessarily satisfactory.
As described above, compounds having a Pxe2x95x90N bond such as a phosphazene compound, phosphazenium compound and the like, are extremely useful as a catalyst for producing a polyoxyalkylene polyol having excellent properties such as low Cxe2x95x90C content, high Hxe2x80x94T bond selectivity and sharp molecular weight distribution of a polyol which is a main reaction component. Therefore, there is desired a method for purifying in a simpler process a polyoxyalkylene polyol produced by using the above-described compound as a catalyst.
In view of the above-described problems, the object of the present invention is to provide a method for producing a polyoxyalkylene polyol which can remove a remaining catalyst compound efficiently by a simple manner from a crude polyoxyalkylene polyol, and a method for producing derivatives thereof.
The present inventors have intensively investigated solving the above-described problems, and as a result, found that a polyoxyalkylene polyol having a low catalyst-remaining amount is obtained by producing a crude polyoxyalkylene polyol by addition polymerization of an epoxide compound to an active hydrogen compound using as a catalyst a compound having a Pxe2x95x90N bond, and further, purifying the resulting crude polyoxyalkylene polyol using a solid acid (adsorbent) having specific form, and completed the present invention.
Namely, the first aspect of the present invention is a method for producing a polyoxyalkylene polyol wherein a crude polyoxyalkylene polyol is produced by addition polymerization of an epoxide compound to an active hydrogen compound using as a catalyst a compound having a Pxe2x95x90N bond, then, the crude polyoxyalkylene polyol is allowed to contact with a solid acid having a specific surface area of 450 to 1200 m2/g and an average pore diameter of 40 to 100 xc3x85 to control the catalyst-remaining amount in the polyoxyalkylene polyol to 150 ppm or less.
Preferable embodiments of the first invention include the above-described method for producing a polyoxyalkylene polyol in which 0.1 to 10% by weight of water is allowed to coexist based on the crude polyoxyalkylene polyol when the crude polyoxyalkylene polyol is allowed to contact with a solid acid, and the above-described method for producing a polyoxyalkylene polyol in which after the crude in polyoxyalkylene polyol is allowed to contact with a solid acid, the solid acid is separated from the polyoxyalkylene polyol, then, at least one acid selected from inorganic acids and organic acids is added in an amount of 1 to 25 ppm based on the polyoxyalkylene polyol. The temperature when the crude polyoxyalkylene polyol is allowed to contact with a solid acid is preferably from 50 to 150xc2x0 C. Further, the catalyst-remaining amount in the purified polyoxyalkylene polyol is preferably controlled to 90 ppm or less.
As the solid acid in the above-described first invention, composite metal oxides are listed which are prepared from different oxides including silicon oxide, boron oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide, calcium oxide and zinc oxide. Specifically, at least one composite metal oxide is listed selected from aluminum silicate, magnesium silicate, zirconium silicate, titanium silicate, calcium silicate, zinc silicate, aluminum borate, magnesium borate, zirconium borate, titanium borate, aluminum zirconate and magnesium zirconate. Among them, aluminum silicate, magnesium silicate and mixtures thereof are a preferable.
As the compound having a Pxe2x95x90N bond, at least one compound is listed selected from phosphazenium compounds, phosphine oxide compounds and phosphazene compounds.
As the phosphazenium compound, compounds represented by the chemical formula (1)
[CF1]
[wherein, a, b, c and d each represents a positive integer from 0 to 3, however, a, b, c and d are not simultaneously 0. Rs are the same or different and represent a hydrocarbon group having 1 to 10 carbon atoms, and in some cases, two Rs on the same nitrogen atom may bond to each other to form a ring structure. Qxe2x88x92 represents a hydroxy anion, alkoxy anion, aryloxy anion or carboxy anion.] are listed.
As the phosphine oxide compound, compounds represented by the chemical formula (2)
[CF2]
[wherein, Rs are the same or different and represent a hydrocarbon group having 1 to 10 carbon atoms, and x represents the amount of water contained in terms of molar ratio and is from 0 to 5.] are listed.
As the phosphazene compound, compounds represented by the chemical formula (3)
[CF3]
[wherein, 1, m and n each represents a positive integer from 0 to 3. Ds are the same or different and represent a hydrocarbon group having 1 to 20 carbon atoms, alkoxy group, phenoxy group, thiophenol residual group, mono-substituted amino group, di-substituted amino group, or a 5 to 6-membered cyclic amino group. Q represents a hydrocarbon group having 1 to 20 carbon atoms. Further, two Ds on the same phosphorus atom or different two phosphorus atoms may bond to each other and D and Q may bond to each other to form ring structures, respectively.] are listed.
As the above-described method for producing a crude polyoxyalkylene polyol, there is a method in which an epoxide compound is addition-polymerized to an active hydrogen compound in the presence of 1xc3x9710xe2x88x924 to 5xc3x9710xe2x88x921 mol of a catalyst based on 1 mol of the active hydrogen compound under conditions of a reaction temperature of 15 to 130xc2x0 C. and a maximum reaction pressure of 882 kPa or less.
Regarding properties of a polyoxyalkylene polyol produced by the method of the present invention, a hydroxyl value is from 2 to 200 mg KOH/g, a total unsaturation degree is 0.07 meq./g or less, and a head-to-tail bond selectivity of an oxypropylene group in a polyoxyalkylene polyol by propylene oxide addition polymerization is 95 mol % or more. In addition to these properties, it is preferable that the content of an oxypropylene group is at least 50% by weight. Further, it is preferable that a hydroxyl value is from 9 to 120 mg KOH/g, a total unsaturation degree is 0.05 meq./g or less, a head-to-tail bond selectivity is 96 mol % or more, and the remaining amount of a catalyst composed of a compound having a Pxe2x95x90N bond is 90 ppm or less.
The second invention is a method for producing a polymer-dispersed polyol wherein polymer particles are dispersed in a polyoxyalkylene polyol, in which the polyoxyalkylene polyol is produced by the above-described production method, then, 5 to 86 parts by weight of an ethylenically-unsaturated monomer is polymerized in 100 parts by weight of the polyoxyalkylene polyol at a temperature from 40 to 200(copyright) in the presence of a radical polymerization initiator to control the concentration of polymer particles to 5 to 60% by weight. The ethylenically-unsaturated monomer is preferably at least one monomer selected from acrylonitrile, styrene, acrylamide and methyl methacrylate.
The third invention is a method for producing an isocyanate group-ended prepolymer wherein a polyoxyalkylene polyol and a polyisocyanate are reacted, in which the polyoxyalkylene polyol is produced by the above-described production method, then, the polyisocyanate is reacted with the resulting polyoxyalkylene polyol at a temperature from 50 to 120(copyright) so as to obtain an isocyanate index of 1.3 to 10, to obtain an isocyanate group-ended prepolymer having an isocyanate group content (NCO %) of 0.3 to 30% by weight and a head-to-tail bond selectivity of a main chain in the prepolymer of 95 mol % or more. It is preferable that the content of a free isocyanate compound in the resulting prepolymer is 1% by weight or less.
The fourth invention is a method for producing an isocyanate group-ended prepolymer wherein a polymer-dispersed polyol and a polyisocyanate are reacted, in which the polymer-dispersed polyol is produced by the above-described production method, then, the polyisocyanate is reacted with the resulting polymer-dispersed polyol at a temperature from 50 to 120(copyright) so as to obtain an isocyanate index of 1.3 to 10, to obtain an isocyanate group-ended prepolymer having an isocyanate group content (NCO %) of 0.3 to 30% by weight.
The fifth invention is a method for producing a polyurethane resin, in which an isocyanate group-ended prepolymer is produced by the above-described method, then, the resulting isocyanate group-ended prepolymer and a chain extender are reacted at a temperature from 60 to 140xc2x0 C. so as to obtain an isocyanate index of 0.6 to 1.5.
The sixth invention is a method for producing a polyurethane resin, in which a polyoxyalkylene polymer is produced by the above-described method, then, the resulting polyoxyalkylene polymer and an isocyanate group-ended prepolymer are reacted at a temperature from 10 to 50xc2x0 C. so as to obtain an isocyanate index of 0.8 to 1.3.
The seventh invention is a method for producing a flexible polyurethane foam wherein a polyol containing a polyoxyalkylene polyol and a polyisocyanate are reacted in the presence of water, a catalyst and surfactant, in which the polyoxyalkylene polyol is produced by the above-described method, then, the polyol containing the resulting polyoxyalkylene polyol in an amount of at least 30% by weight in the polyol is used.
The eighth invention is a method for producing a flexible polyurethane foam wherein a polyol containing a polymer-dispersed polyol and a polyisocyanate are reacted in the presence of water, a catalyst and surfactant, in which the polymer-dispersed polyol is produced by the above-described method, then, the polyol containing the resulting polymer-dispersed polyol in an amount of at least 10% by weight in the polyol is used.
The characteristic of the present invention resides in a procedure in that a crude polyoxyalkylene polyol is produced using as a catalyst a compound having a Pxe2x95x90N bond, and a remaining catalyst is removed by allowing the resulting crude polyoxyalkylene polyol to contact with a solid acid having a specific form to control the catalyst-remaining amount in the crude polyoxyalkylene polyol to 150 ppm or less.
The purification method using a solid acid of the present invention manifests lower product loss in the purification a process since neutralization treatment with an acid and the an like are not required and consequently the process can be simplified as compared with a conventional purification method using a solid acid (adsorbent). Also, due to a lower remaining amount of a catalyst, there is an advantage in that storage stability of an isocyanate group-ended prepolymer which is a derivative of a polyoxyalkylene polyol is improved. Further, properties of a polyurethane obtained by the prepolymer are also excellent.
According to the present invention, a polyoxyalkylene polyol of high purity can be produced easily by a simple method requiring no complicated process. Further, by applying the method for producing a polyoxyalkylene polyol of the present invention, there can be easily produced a polymer-dispersed polyol, isocyanate group-ended prepolymer, flexible polyurethane foam and polyurethane resin which are derivatives thereof.
The catalyst-remaining amount can be efficiently controlled to 150 ppm or less, by producing a crude polyoxyalkylene polyol using as a catalyst a compound having a Pxe2x95x90N bond, especially, a compound represented by any of the above-described chemical formulae (1) through (3), and purifying the resulting crude polyoxyalkylene polyol with a solid acid a having specific form. Therefore, a polyoxyalkylene polyol of high quality having low impurity content can be produced. By controlling the catalyst-remaining amount in a polyol to 150 ppm or less, the storage stability of an isocyanate group-ended prepolymer obtained by reacting a polyol with a polyisocyanate compound increases. Further, a polyoxyalkylene polyol obtained by the present invention has low viscosity and has low monool content due to increased Hxe2x80x94T bond selectivity.
A composite metal cyanide complex catalyst is known to act in producing a polyoxyalkylene polyol having low Cxe2x95x90C content. However, this catalyst cannot be used in conducting addition-polymerization of ethylene oxide. Therefore, in addition-polymerization of ethylene oxide, changing to another catalyst is necessary and a complicated reaction operation is required. On the other hand, a catalyst composed of a compound having a Pxe2x95x90N bond used in the present invention required no complicated reaction operation as described above. When a phosphine oxide compound (PZO) is used as a catalyst among compounds having a Pxe2x95x90N bond, if the water content in an active hydrogen compound and catalyst is 600 ppm or less in a process for preparing a polymerization initiator for a polyoxyalkylene polyol, dehydration operation, de-salting operation and the like are not necessary. Therefore, the productivity of a polyoxyalkylene polyol increases.
A polymer-dispersed polyol produced by the method of the present invention is obtained by using as a dispersion medium a polyoxyalkylene polyol having a low catalyst-remaining amount and low monool content and having high Hxe2x80x94T bond selectivity. Therefore, it has low viscosity. Consequently, even if the polymer particle concentration is raised, there can be produced a polymer-dispersed polyol having low viscosity and having excellent dispersion stability of a particle as compared with a conventional product.
An isocyanate group-ended prepolymer produced by the method of the present invention is obtained by using a polyoxyalkylene polyol having a low catalyst-remaining amount and low monool content and having high Hxe2x80x94T bond selectivity, therefore, it manifests excellent abilities in mechanical property, and its exhibiting property and exterior form even in a wide range of polyurethane uses. In addition, the isocyanate group-ended prepolymer is also excellent in storage stability.
Further, a flexible polyurethane foam produced by the method of the present invention provides excellent durability in compression set, wet thermal compression set, repeated compression testing and the like, in addition to excellent molding property.
Therefore, the methods for producing a polyoxyalkylene polyol and a derivative thereof of the present invention are extremely useful methods for producing raw materials in polyurethane fields such as paints, adhesives, floor materials, sealing materials, shoe soles, elastomers and the like, surfactants, lubricants, hydraulic fluids, and sanitary products, and the like.
The present invention will be described in detail below.
 less than Production Method of Polyoxyalkylene Polyol greater than 
A method for producing a polyoxyalkylene polyol of the present invention will be first described.
In the method for producing a polyoxyalkylene polyol of the present invention, a crude polyoxyalkylene polyol is produced by addition polymerization of an epoxide compound to an active hydrogen compound using as a catalyst a compound having a Pxe2x95x90N bond, then, the resulting crude polyoxyalkylene polyol is purified by contact with a solid acid having a specific form.
As the compound having a Pxe2x95x90N bond used as a catalyst for producing a crude polyoxyalkylene polyol, there are listed phosphazenium compounds, phosphine oxide compounds and phosphazene compounds.
As the phosphazenium compound, compounds represented by the above-described chemical formula (1) or compounds represented by the chemical formula (4) 
[wherein, a, b, c and d each represents a positive integer from 0 to 3, however, a, b, c and d are not simultaneously 0. Rs are the same or different and represent a hydrocarbon group having 1 to 10 carbon atoms, and in some cases, two Rs on the same nitrogen atom may bond to each other to form a ring structure. r is an integer from 1 to 3 and represents the number of phosphazenium cations, and Trxe2x88x92 represents an inorganic anion having a valency of r.] are listed.
Among these compounds, it is preferable that the compound is represented by the chemical formula (1) are preferable.
Each of a, b, c and d in a phosphazenium cation represented by the chemical formula (1) or the chemical formula (4) in the present invention is a positive integer from 0 to 3. Herein, they are not simultaneously 0. An integer from 0 to 2 is preferable. Preferably they are represented by combination (2,1,1,1), (1,1,1,1), (0,1,1,1), (0,0,1,1) or (0,0,0,1) irrespective of order of a, b, c and d. More preferably they are represented by combination (1,1,1,1), (0,1,1,1), (0,0,1,1) or (0,0,0,1).
Rs in a phosphazenium cation represented by the chemical formula (1) or the chemical formula (4) in the present invention are the same or different and represent a hydrocarbon atom having 1 to 10 carbon atoms. Specifically, this R is selected from aliphatic or aromatic hydrocarbon groups such as, for example, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, tert-butyl, 2-butenyl, 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, isopentyl, tert-pentyl, 3-methyl-2-butyl, neopentyl, n-hexyl, 4-methyl-2-pentyl, cyclopentyl, cyclohexyl, 1-heptyl, 3-heptyl, 1-octyl, 2-octyl, 2-ethyl-1-hexyl, 1,1-dimethyl-3,3-dimethylbutyl (tert-octyl), nonyl, decyl, phenyl, 4-toluyl, benzyl, 1-phenylethyl, 2-phenylethyl and the like. Of them, aliphatic hydrocarbons having 1 to 10 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, tert-pentyl, tert-octyl and the like are preferable. A methyl group or ethyl group is more preferable.
When two Rs on the same nitrogen atom in a phosphazenium cation bond to form a ring structure, the divalent hydrocarbon group on the nitrogen atom is a divalent hydrocarbon group having a main chain composed of 4 to 6 carbon atoms (the ring is a 5 to 7-membered ring containing the nitrogen atom). Preferably, examples are tetramethylene, pentamethylene, hexamethylene and the like. Also, compounds obtained by substitution with an alkyl group such as methyl, ethyl and the like on the main chain are examples. Tetramethylene or the pentamethylene group is more preferable. All or a part of possible nitrogen atoms in a phosphazenium cation may form such ring structures.
Trxe2x88x92 in the chemical formula (4) represents an inorganic anion having a valency of r. r is an integer from 1 through 3. Examples of such an inorganic anion include boric acid, tetrafluoric acid, hydrocyanic acid, thiocyanic acid; hydrohalogenic acid such as hydrofluoric acid, hydrochloric acid, hydrobromic acid or the like; nitric acid, sulfuric acid, phosphoric acid, phosphorus acid, hexafluorophosphoric acid, carbonic acid, hexafluoroantimonic acid, hexafluorothalliumic acid, perchloric acid and the like. As the inorganic anion, there are also HSO4xe2x88x92 and HCO3xe2x88x92. These inorganic anions can be exchanged mutually by an ion exchange reaction. Among these inorganic anions, anions of inorganic acids such as boric acid, tetrafluoroboric acid, hydrohalogenic acid, phosphoric acid, hexafluorophosphoric acid, perchloric acid and the like are more preferable. Chrorine anion is preferable still.
When a phosphazenium compound represented by the chemical formula (4) is used as a catalyst, it is necessary to previously prepare a salt of an alkaline metal or alkaline earth metal of an active hydrogen compound. The preparation method of this salt may be a conventionally known method. As the salt of an alkaline metal or alkaline earth metal of an active hydrogen compound to be allowed to coexist with a compound represented by the formula (4) is a salt in which an active hydrogen in an active hydrogen compound is dissociated as a hydrogen ion and is substituted by an alkaline metal or alkaline earth metal ion.
Examples of preferable embodiments of a compound represented by the chemical formula (1) include tetrakis[tris(dimethylamino)phosphoranylideneamino]phospho nium hydroxide, tetrakis[tris(dimethylamino)phosphoranylideneamino]phospho nium methoxide, tetrakis[(tris(dimethylamino)phosphoranylideneamino]phospho nium ethoxide, tetrakis[tri(pyrrolidine-1-yl)phosphoranylideneamino]phosphoniumtert-butoxide, and the like.
As the phosphine oxide compound, compounds represented by the above-described chemical formula (2) are listed. Rs in a phosphine oxide compound represented by the chemical formula (2) are the same or different and represent a hydrocarbon atom having 1 through 10 carbon atoms. This R is selected from aliphatic or aromatic hydrocarbon groups such as, for example, methyl, ethyl, n-propyl, isopropyl, allyl, n-butyl, sec-butyl, tert-butyl, 2-butenyl, 1-pentyl, 2-pentyl, 3-pentyl, 2-methyl-1-butyl, isopentyl, tert-pentyl, 3-methyl-2-butyl, neopentyl, n-hexyl, 4-methyl-2-pentyl, cyclopentyl, cyclohexyl, 1-heptyl, 3-heptyl, 1-octyl, 2-octyl, 2-ethyl-1-hexyl, 1,1-dimethyl-3,3-dimethylbutyl (under the name of tert-octyl), nonyl, decyl, phenyl, 4-toluyl, benzyl, 1-phenylethyl, 2-phenylethyl and the like. Further, R may be in the form of a pyrrolidino group or pyperidino group. Of them, the same or different aliphatic hydrocarbon groups having 1 through 8 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, tert-butyl, tert-pentyl, 1-dimethyl -3,3-dimethylbutyl and the like are preferable. A methyl group or ethyl group is more preferable.
A phosphine oxide compound represented by the chemical formula (2) can be synthesized by a method described in the Journal of General Chemistry of the USSR, Vol. 55, p. 1453 (1985) or by an analogous method. Usually, a phosphine oxide compound represented by the chemical formula (2) has a hygroscopic property, and tends to become a water-containing material or a hydrate. x showing the amount of a water molecule contained in a phosphine oxide compound is represented in terms of molar ratio based on this phosphine oxide compound, and x is from 0 through 5 and preferably from 0 through 2.
Preferable embodiments of a phosphine oxide compound include tris[tris(dimethylamino)phosphoranylideneamino]phosphine oxide or tris[tris(diethylamino)phosphoranylideneamino]phosphine oxide and the like.
As the phosphazene compound, compounds shown in Japanese Laid-Open Patent Publication (JP-A) No. Hei-10-36499 of a patent application by the present applicant are listed. Specifically, compounds represented by the above-described chemical formula (3) are listed.
Examples of Q in the chemical formula (3), namely a hydrocarbon group having 1 through 20 carbon atoms include alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, tert-octyl, nonyl, decyl and the like; alkyl groups having an unsaturated bond or aromatic group such as allyl, 2-methylallyl, benzyl, phenetyl, o-anisyl, 1-phenylethyl, diphenylmethyl, triphenylmethyl, cinnamyl and the like; alicyclic groups such as cyclopentyl, cyclohexyl, 4-methylcyclohexyl, 3-propylcyclohexyl, 4-phenylcyclohexyl, cycloheptyl, 1-cyclohexenyl and the like; alkenyl groups such as vinyl, styryl, propenyl, isopropenyl, 2-methyl-1-propcnyl, 1,3-butadienyl and the like; alkynyl groups such as ethynyl, 2-propynyl and the like; and aromatic groups such as phenyl, o-tolyl, m-tolyl, p-tolyl, 2,3-xylyl, 2,4-xylyl, 3,4-xylyl, mesityl, o-cumenyl, m-cumenyl, p-cumenyl, 1-naphthyl, 2-naphthyl, p-methoxyphenyl and the like.
Examples of D in the chemical formula (3), namely a hydrocarbon group having 1 through 20 carbon atoms include alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, ncopentyl, hexyl, heptyl, octyl, tert-octyl, nonyl, decyl and the like; alkyl groups having an unsaturated bond or aromatic group such as allyl, 2-methylallyl, benzyl, phenetyl, o-anisyl, 1-phenyletliyl, diphenylmethiyl, triphenylmethyl, cinnamyl and the like; alicyclic groups such as cyclopentyl, cyclohexyl, 4-methylcyclohexyl, 3-propylcyclohexyl, 4-phenylcyclohexyl, cycloheptyl, 1-cyclohexenyl and the like; alkenyl groups such as vinyl, styryl, propenyl, isopropenyl, 2-methyl-1-propenyl, 1,3-butadienyl and the like; alkynyl groups such as ethynyl, 2-propynyl and the like; and aromatic groups such as phenyl, o-tolyl, m-tolyl, p-tolyl, 2,3-xylyl, 2,4-xylyl, 3,4-xylyl, mesityl, o-cumenyl, m-cumenyl, p-cumenyl, 1-naphthyl, 2-naphthyl, p-niethoxyphenyl and the like.
The alkoxy group represented by D is an alkoxy group having 1 through 20 carbon atoms such as, for example, methoxy, ethoxy, propoxy, isopropoxy, butoxy, pentyloxy, allyloxy, cyclohexyloxy, benzyloxy and the like, the phenoxy group represented by D is a phenoxy group having 6 through 20 carbon atoms such as, for example, phenoxy, 4-methylphenoxy, 3-propylphenoxy, 1-naphthyloxy and the like, the thiol residue represented by D is a thiol residue having 1 through 20 carbon atoms such as, for example, methylthio, ethylthio, propylthio, isopropylthio, butylthio, isobutylthio, tert-butylthio, pentylthio, hexylthio, heptylthio, octylthio, tert-octylthio, nonylthio, decylthio and the like.
The thiophenol residue represented by D is a thiophenol residue having 6 through 20 carbon atoms such as, for example, phenylthio, o-toluylthio, m-toluylthio, p-toluylthio, 2,3-xylylthio, 2,4-xylylthio, 3,4-xylylthio, 4-ethylphenylthio, 2-naphthylthio and the like; and the mono-substituted amino group represented by D is a mono-substituted amino group having 1 through 20 carbon atoms such as, for example, methylamino, ethylamino, propylamino, isopropylamino, butylamino, isobutylamino, tert-butylamino, pentylamino, hexylamino, heptylamino, octylamino, tert-octylamino, nonylamino, decylamino, 1-ethylpropylamino, 1-ethylbutylamino, anilino, o-toluylamino, m-toluylamino, p-toluylamino, 2,3-xylynoamino, 2,4-xylynoamino, 3,4-xylynoamino and the like.
The di-substituted amino group represented by D is an amino group di-substituted with the same or different hydrocarbon groups having 1 through 20 carbon atoms such as, for example, diniethylamino, diethylamino, methylethylamino, dipropylamino, metilylpropylamino, diisopropylamino, dibutylamino, methylbutylamino, diisobutylamino, di-sec-butylamino, dipentylamino, dihexylamino, ethylhexylamino, dilheptylamino, dioctylamino, di-tert-octylamino, ethyl-tert-octylamino, dinonylamino, didecylamino, diphenylamino, methylphenylamino, ethylphenylamino, di-o-toluylamino, di-2,3-xylylamino, phenyltoluylamino and the like, and there arc listed 5 to 6-membered cyclic amino groups such as 1-pyrrolidinyl, 3-methyl-1-pyrrolidinyl, 1-pyrrolyl, 3-ethyl-1-pyrrolyl, 1-indolyl, 1-piperidyl, 3-metlhyl-1-piperidyl, 1-piperazinyl, 4-methyl-1-piperazinyl, 1-imidazolydinyl, 4-morpholinyl and the like.
When two Ds on the same phosphorus atom or on two different phosphorus atoms bond to form a possible whole or partial ring structure, the divalent group (Dxe2x80x94D) on a phosphorus atom is a saturated or unsaturated aliphatic divalent hydrocarbon group such as ethylene, vinylene, propylene, 1,2-cyclohexanylene, 1,2-phenylene, trimethylene, propenylene, tetramethylene, 2,2xe2x80x2-biphenylene, 1-butenylene, 2-butenylene, pentamethylene and the like.
Further, there are listed divalent groups in which any one or two selected from the group consisting of an oxygen atom, sulfur atom and hydrogen atom or a nitrogen atom to which an aliphatic or aromatic hydrocarbon group such as a methyl group, ethyl group, butyl group, cyclohexyl group, benzyl group, phenyl group and the like is bonded are inserted into one or both of the bonds between the both ends of the divalent group and a phosphorus atom.
Specific examples of the divalent group include methyleneoxy, ethylene-2-oxy, trimethylene-3-oxy, methylenedioxy, ethylenedioxy, trimethylene-1,3-dioxy, cyclohexane-1,2-dioxy, benzene-1,2-dioxy, methylenethio, ethylene-2-thio, trimethylene-3-thio, tetramethylene-4-thio, methylenedithio, ethylenedithio, trimethylene-1,3-dithio, iminomethylene, 2-iminoethylene, 3-iminotrimethylene, 4-iminotetramethylene, N-ethyliminomethylene, N-cyclohexyl-2-iminoethylene, N-methyl-3-iminotrimethylene, N-benzyl-4-iminotetramethylene, diiminomethylene, 1,2-diiminoethylene, 1,2-diiminovinylene, 1,3-diiminotrimethylene, N,Nxe2x80x2-dimethyldiiminomethylene, N,Nxe2x80x2-diphenyl-1,2-diiminoethylene, N,Nxe2x80x2-dimethyl-1,2-diiminoethylene, N-methyl-Nxe2x80x2-ethyl-1,3-diiminotrimethylene, N,Nxe2x80x2-diethyl-1,4-diiminotetramethylene, N-methyl-1,3-diiminotrimethylene and the like.
When D and Q bond to each other to form a possible whole or partial ring structure, the divalent group (Dxe2x80x94Q) connecting a nitrogen atom and a phosphorus atom is the same saturated or unsaturated aliphatic divalent hydrocarbon group as the divalent group on a phosphorus atom described above, and there are listed divalent groups in which any one selected from the group consisting of an oxygen atom, sulfur atom and hydrogen atom or a nitrogen atom to which an aliphatic or aromatic hydrocarbon group such as a methyl group, ethyl group, butyl group, cyclohexyl group, benzyl group, phenyl group and the like is bonded is inserted into a bond between the divalent hydrocarbon group and a phosphorus atom.
Specific examples of the divalent group include methyleneoxy, ethylene-2-oxy, methylenethio, ethylene-2-thio, iminomethylene, 2-iminoethylene, N-methyliminomethylene, N-ethyl-2-iminotriethylene, N-methyl-3-iminotrimethylene, N-phenyl-2-iminoethylene and the like.
Regarding specific examples of a phosphazene compound having a structure represented by the chemical formula (3), examples thereof when Ds are the same or different alkyl groups include 1-tert-butyl-2,2,2-trimethylphosphazene, 1-(1,1,3,3-tetramethylbutyl)-2,2,4,4,4-pentaisopropyl-2xcex5,4xcex5-catenadi(phosphazene) and the like.
Examples thereof when D is an alkyl group having an unsaturated bond or an aromatic group include 1-tert-butyl-2,2,2-triallylphosphazene, 1-cyclohexyl-2,2,4,4,4-pentaallyl-2xcex5,4xcex5-catenadi(phosphazene), 1-ethyl-2,4,4,4-tribenzyl-2-tribenzylphosphoranylideneamino-2xcex5,4xcex5-catenadi(phosphazene), and the like.
Examples thereof when D is an alicyclic group include 1-methyl-2,2,2-tricyclopcntylphosphazene, 1-propyl-2,2,4,4,4-cyclohexyl-2xcex5,4xcex5-catenadi(phosphazene), and the like. Examples thereof when D is an alkenyl group include 1-butyl-2,2,2-trivinylphosphazene, 1-tert-butyl-2,2,4,4,4-pentastyryl-2xcex5,4xcex5-catenadi(phospihazene), and the like. Examples thereof when D is an alkynyl group include 1-tert-butyl-2,2,2-tri(2-phenylethynyl)phosphiazene, and the like, and examples thereof when D is an aromatic group include 1-isopropyl-2,4,4,4-tetraphenyl-2-triphenylphosphoranylideneamino-2xcex5,4xcex5-catenadi(phosphazene), and the like.
Examples thereof when D is an alkoxy group include 1-tert-butyl-2,2,2-trimethoxyphosphazene, 1-(1,1,3,3-tetramethylbutyl)-2,2,4,4,4-pentaisopropoxy-2xcex5,4xcex5-catenadi(phosphazene) or 1-phenyl-2,2,4,4,4-pentabenzyloxy-2xcex5,4xcex5-catenadi(phosphazene), and the like. Examples thereof when D is a phenoxy group include 1-methyl-2,2,2-triphenoxyphosphazene, 1-tert-butyl-2,2,4,4,4-penta(1-naphthyloxy)-2xcex5,4xcex5-catenadi(phosphazene), and the like.
Examples thereof when D is a di-substituted amino group include 1-tert-butyl-2,2,2-tris(dimethylamino)phosphazene, 1-(1,1,3,3-tetramethylbutyl)-2,2,2-tris(dimethylamino)phosphazene, 1-ethyl-2,2,4,4,4-pentakis(dimethylamino)-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-2,4,4,4-tetrakis(dimethylamino)-2-tris(dimethylamino)phosphoranylideneamino-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-2,4,4,4-tetrakis(diisopropylamino)-2-tris(diisopropylamino)phosphoranylideneamino-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-2,4,4,4-tetrakis(di-n-butylamino)-2-tris(di-n-butylamino)phosphoranylideneamino-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylideneamino]-2xcex5,4xcex5-catenadi(phosphazene), 1-(1,1,3,3-tetramethylbutyl)-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylideneamino]-2xcex5,4xcex5-catenadi(phosphazene), 1-(1,1,3,3-tetramethylbutyl)-4,4,4-tris(methylethylamino)-2,2-bis[tris(methylethylamino)phosphoranylideneamino]-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-4,4,4-tris(diethylamino)-2,2-bis[tris(diethylamino)phosphoranylideneamino]-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-4,4,4-tris(diisopropylamino)-2,2-bis[tris(diisopropylamino)phosphoranylideneamino]-2xcex5,4xcex5-catenadi(phosphazene), 1-tert-butyl-4,4,4-tris(di-n-butylamino)-2,2-bis[tris(di-n-butylarnino)phosphoranylideneamino]-2xcex5,4xcex5,65-catenadi(phosphazene), 1-tert-butyl-4,4,6,6,6-pentakis(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylideneamino)]-2xcex5,4xcex5,6xcex5-catenatri(phosphazene), 1-tert-butyl-4,4,6,6,6-pentakis(dimethylamino)-2,2-bis[tris(diethylamino)phosphoranylideneamino]-2xcex5,4xcex5,65-catenatri(phosphazene), 1-tert-butyl-4,4,6,6,6-pentakis(diisopropylamino)-2,2-bis[(tris(diisopropylamino)phosphoranylideneamino]-2xcex5,4xcex5,65-catenatri(phosphazene), 1-tert-butyl-4,4,6,6,6-pentakis(di-n-butylamino)-2,2-bis[tris(di-n-butylamino)phosphoranylideneamino]-2xcex5,4xcex5,65-catenatri(phosphazene), 1-tert-butyl-4,4,6,6,6-pentakis(dimethylamino)-2-[2,2,2-tris(dimethylamino)phosphazene-1-yl]-2-[2,2,4,4,4-pentakis(dimethylamino)-2xcex5,4xcex5-catenadi(phosphazene)-1-yl]-2xcex5,4xcex5,65-catenatri(phosphazene), 1-phenyl-2,2-bis(dimethylamino)-4,4-dimethoxy-4-phenylamino-2xcex5,4xcex5-catenadi(phosphazene), and the like.
Further, when Ds on the same phosphorus atom or two different phosphorus atoms bond to each other to form a ring structure, examples thereof include 2-(tert-butylimino)-2-dimethylamino-1,3-dimethyl-1,3-diaza-2xcex5-phosphinane, and the like.
Examples of preferable embodiments of a phosphazene compound include 1-tert-butyl-2,2,2-tris(dimethylamino)phosphazene, 1-(1,1,3,3-tetrametliylbutyl)-2,2,2-tris(dimethylamino)phospliazene, 1-ethyl-2,2,4,4,4-pntakis(dimethylamino)-2xcex5,4xcex5-catenadi(phosphazene), 1 1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis-2xcex5,4xcex5-catenadi(phosphazen), 1-(1,1,3,3-tetramethylbutyl)-4,4,4-tris(diniethylaniino)-2,2-bis-2xcex5,4xcex5-catenadi(phosphazen e), 1-tert-butyl-2,2,2-tri(1-pyrrolidinyl)phosphazene, 7-ethyl-5,11-dimethyl-1,5,7,11-tetraaza-6xcex5-phosphaspiroundeca-1(6)-ene, and the like. Of the compounds having a Pxe2x95x90N bond as described above in detail, phosphazenium compound, phosphine oxide compound and mixtures thereof are preferable in view of industrial applicability of the catalyst.
As the active hydrogen compound used in the present invention, alcohols, phenol compounds, polyamines, alkanolamines, thioalcohols and the like are listed. Examples thereof include water, divalent alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,5-pentanediol, neopentyl glycol, 2-methyl-1,5-pentanediol, 2-ethyl-1,4-butanediol, 1,4-dimethylolcyclohexane, 1,3-propanediol, 1,4-cyclohexanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexanediol and the like, alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and the like, polyhydric alcohols such as glycerine, diglycerine, trimethylolpropane, trimethylolethane, trimethylolbutane, ditrimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol and the like, saccharides such as glucose, sorbitol, dextrose, fructose, saccharose, methylglucoside and the like, or derivatives thereof, fatty amines such as ethylenediamine, di(2-aminoethyl)amine, hexamethylenediamine and the like, aromatic amines such as toluylenediamine, diphenylmethanediamine and the like, phenol compounds such as bisphenol A, bisphenol F, bisphenol S, novolak, resol, resorcine and the like, as well as other compounds.
Further, there are listed divalent thioalcohols such as ethylenethioglycol, propylenethioglycol, trimethylenethioglycol, butanedithiol and the like, and alkylenethioglycols such as diethylenethioglycol, triethylenethioglycol and the like. These active hydrogen compounds can also be used in combination of two or more.
Further, there can also be used compounds obtained by addition-polymerization of an epoxide compound to these active hydrogen compounds by a conventionally known method.
Of these compounds, most preferable are divalent alcohols, compounds having an average molecular weight of up to 2000 obtained by addition-polymerization of an alkylene oxide to divalent alcohols, trivalent alcohols, and compounds having an average molecular weight of up to 2000 obtained by addition-polymerization of an alkylene oxide to trivalent alcohols. Compounds having an average molecular weight of over 2000 after addition of an epoxide compound to divalent alcohols or trivalent alcohols are not preferable due to increased amounts of by-produced monools.
As the epoxide compound to be addition-polymerized to the above-described active hydrogen compound, propylene oxide, ethylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, styrene oxide, cyclohexene oxide, epichlorohydrin, epibromohydrin, methyl glycidyl ether, allyl glycidyl ether and the like are listed. These may be used in combination of two or more. Of them, preferable are propylene oxide, ethylene oxide, 1,2-butylene oxide, 2,3-butylene oxide and styrene oxide. More preferable are propylene oxide and ethylene oxide. It is preferable that propylene oxide occupies at least 50% by weight of the total amount of epoxide compounds. This proportion is more preferably at least 60t by weight, and preferably still at least 70% by weight. By using an epoxide compound containing such proportion of propylene oxide, the amount of an oxypropylene group in a polyoxyalkylene polyol can be controlled to at least 50% by weight. The suitable content of an oxypropylene group is at least 60% by weight, preferably still, at least 70% by weight. When the content of an oxypropylene group is 50% by weight or more, the viscosity of a polyoxyalkylene polyol decreases and the flexibility of an urethane resin obtained from this polyol is improved.
The amount used of the above-described compound having a Pxe2x95x90N bond which is a catalyst is from 1xc3x9710xe2x88x924 to 5xc3x9710xe2x88x921 mol based on 1 of an active hydrogen compound. It is preferably from 5xc3x9710xe2x88x924 to 1xc3x9710xe2x88x921 mol, more preferably from 1xc3x9710xe2x88x923 to 1xc3x9710xe2x88x922 mol. When the molecular weight of a polyoxyalkylene polyol is increased, the concentration of a compound having a Pxe2x95x90N bond in an active hydrogen compound is preferably increased in the above-described range. When the amount of a compound having a Pxe2x95x90N bond is less than 1xc3x9710xe2x88x924 mol based on 1 mol of an active hydrogen compound, the polymerization speed of an epoxide compound decreases and the production time of a polyoxyalkylene polyol is elongated. Conversely, when over 5xc3x9710xe2x88x921 mol, the cost of a catalyst composed of a compound having a Pxe2x95x90N bond occupying in the production cost of a polyoxyalkylene polyol increases.
The temperature at which an epoxide compound is addition-polymerized to an active hydrogen compound is from 15 to 30xc2x0 C. It is in the range preferably from 40 to 120xc2x0 C., preferably still from 50 to 110xc2x0 C. When the addition-polymerization of an epoxide compound is conducted at a lower temperature in the above-described range, it is preferable to raise the concentration of a compound having a Pxe2x95x90N bond in an active hydrogen compound in the above-described range. When the addition-polymerization temperature of an epoxide compound is lower than 15xc2x0 C., the polymerization speed of an epoxide compound lowers leading to elongation of the production time of a polyoxyalkylene polyol. On the other hand, when the addition-polymerization temperature is over 130xc2x0 C., the total unsaturation degree (Cxe2x95x90C) increased over 0.07 meq./g, though it is dependent on the hydroxyl value (OHV) of a polyoxyalkylene polyol.
The maximum pressure in the addition-polymerization reaction of an epoxide compound is 882 kPa or lower. Usually, the addition-polymerization of an epoxide compound is conducted in a pressure proof reaction apparatus. The reaction of an epoxide compound may be initiated from a reduced pressure condition or from an atmospheric pressure condition. When initiated from an atmospheric pressure condition, it is desirably conducted in the presence of an inactive gas such as nitrogen, helium and the like. When the maximum reaction pressure of an epoxide compound is over 882 kPa, the amount of by-produced monools increases. The maximum reaction pressure is preferably 686 kPa or lower, and preferably still at 490 kPa or lower. When propylene oxide is used as the epoxide compound, the maximum reaction pressure is preferably 490 kPa or less.
For feeding an epoxide compound to the polymerization system, a method in which a part of an epoxide compound in a required amount is fed in one portion, and the remaining part is continuously fed, a method in which all of an epoxide compound is continuously fed, and the like are used. In the method in which a part of an epoxide compound in a required amount is fed in one portion, it is preferable that the reaction temperature in the early period of a polymerization reaction of an epoxide compound is at a lower side in the above-described temperature range and after charging of an epoxide compound, the reaction temperature is raised gradually.
As the polymerization method in which propylene oxide and ethylene oxide are used together as epoxide compounds, there are (1) an ethylene oxide cap reaction in which after polymerization of propylene oxide, ethylene oxide is block-copolymerized, (2) a random reaction in which propylene oxide and ethylene oxide are random-copolymerized, and (3) a triblock copolymerization reaction in which after polymerization of propylene oxide, ethylene oxide is polymerized, then, propylene oxide is polymerized. Of these methods, preferable are the ethylene oxide cap method and triblock copolymerization method.
The maximum pressure of an addition-polymerization apparatus is influenced by the charging speed of an epoxide compound, polymerization temperature, amount of a catalyst and the like. The charging speed of an epoxide compound is preferably controlled so that the maximum pressure of an addition-polymerization apparatus does not exceed 882 kPa. When charging of an epoxide compound is completed, the inner pressure of an addition-polymerization apparatus decreases gradually. It is preferable to continue the addition-polymerization reaction until change in the inner pressure is not recognized. When based on the hydroxyl value (OHV) of a polyoxyalkylene polyol, it is preferable to continue the addition-polymerization until OHV becomes 2 through 200 mg KOH/g.
In conducting the addition-polymerization reaction of an epoxide compound, a solvent can also be used if necessary. Examples of the solvent include aliphatic hydrocarbons such as pentane, hexane, heptane and the like, ethers such as diethyl ether, tetrahydrofuran, dioxane and the like, aprotic polar solvents such as dimethylsulfoxide, N,N-dimethylformainide and the like, as well as other compounds. When a solvent is used, it is desirable that the solvent is recovered after production and is recycled so that the production cost of a polyoxyalkylene polyol does not increase.
In the method for producing a polyoxyalkylene polyol using a phosphine oxide compound as a catalyst of the present invention, when water content of an active hydrogen compound (excepting water) and a phosphine oxide compound is low, operation such as heat and pressure-reduced dehydration treatment, de-saltingreaction or the likemaynotbe conducted in a process for preparing a polymerization initiator for a polyoxyalkylene polyol. Usually, in the most widely flourishing method using a KOH catalyst, it is required that before addition-polymerization of an epoxide compound to an active hydrogen compound, KOH and the active hydrogen compound are charged into a reaction apparatus, and heat and pressure-reduced dehydration treatment is conducted under conditions of a temperature of 100 to 120xc2x0 C. and a pressure of 1.33 kPa or less for 3 to 8 hours, to prepare a polymerization initiator (potassium salt of active hydrogen compound). Further, in the method using a phosphazenium compound catalyst in which an inorganic compound described in Japanese Laid-Open Patent Publication (JP-A) No. Hei-10-77289 or International Publication WO 98/54241 (EP 0916686A1) is a counter anion, de-salting reaction with the above-described potassium salt of an active hydrogen compound should be conducted to prepare a polymerization initiator. The water content in the case wherein heat and pressure-reduced dehydration treatment may not be conducted is preferably 600 ppm or less, preferably still 400 ppm or less, and most preferably 300 ppm or less based on the total amount of the active hydrogen compound and phosphine oxide compound.
Next, a method for purifying a crude polyoxyalkylene polyol produced as described above will be described. The main object of the purification resides in removal of a compound having a Pxe2x95x90N bond remaining in the crude polyoxyalkylene polyol. The present inventors have found that by allowing a crude polyoxyalkylene polyol to contact with a solid acid having a particular specific surface area and average pore diameter, the remaining catalyst can be removed efficiently and the remaining amount of the catalyst can be controlled to not more than a particular value. Particularly, a solid acid having a specific surface area of 450 to 1200 m2/g and an average pore diameter of 40 to 100 xc3x85 is useful.
In view of the ability for removing a compound having a Pxe2x95x90N bond (hereinafter, referred to as catalyst), the specific surface area of a solid acid is an important factor. The specific surface area of a solid acid is preferably from 500 to 1100 m2/g, preferably still, from 550 to 1000 m2/g. When the specific surface area is less than 450 m2/g, the ability for removing a catalyst in a crude polyoxyalkylene polyol lowers. On the other hand, in view of efficiency in recovering a crude polyoxyalkylene polyol from a mixed solution of the crude polyoxyalkylene polyol and solid acid, the upper limit of a specific surface area is 1200 m2/g.
The average pore diameter is preferably from 50 to 100 xc3x85, preferably still, from 55 to 95 xc3x85. A solid acid having an average pore diameter of less than 40 xc3x85, for example, zeolite or the like, has lower ability for removing a catalyst. On the other hand, in view of the molecular diameter of a catalyst, specific surface area of a solid acid, and the like, the upper limit of the average pore diameter of the solid acid is 100 xc3x85. Further, for improving the ability for removing a catalyst, it is preferable to use a solid acid having a specific surface area and an average pore diameter within the above-described ranges and a diameter in the range from 10 through 60 xc3x85.
As the solid acid having the above-described form, clay minerals such as acid clay, montmorillonite and the like, composite metal oxides such as aluminum silicate, magnesium silicate and the like, metal sulfate salt or phosphate salt and the like, solidified acids such as silica gel-phosphoric acid, and the like, and cation exchange resins are listed. For the object of the present invention, a composite metal oxide having the above-described specific surface area and average pore diameter is preferable. As such a composite metal oxide, there are listed composite metal oxides prepared using different oxides such as silicon oxide, boron oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide, calcium oxide, zinc oxide and the like. Specifically, aluminum silicate, magnesium silicate, zirconium silicate, titanium silicate, calcium silicate, zinc silicate, aluminum borate, magnesium borate, zirconium borate, titanium borate, aluminum zirconate, magnesium zirconate, and the like. In addition to these composite metal oxides, a single metal oxide substance such as silica gel and the like can be used providing the form described above is satisfied.
Solid acids particularly preferably used include aluminum silicate, magnesium silicate and mixtures thereof. It is preferable that these are synthetic products not natural products. As commercially available products of a solid acid having such properties, KW-600 BUPxe2x80x94S, KW-700 PEL, KW-700 SEL (trade name) and the like manufactured by Kyowa Chemical Industry K.K. are listed. Of them, KW-700 PEL and KW-700 SEL are preferable, and KW-700 SEL is most preferable.
As the synthetic aluminum silicate, those having a silicon dioxide content of 55 to 75% by weight and an aluminum oxide content of 5 to 25% by weight are preferable. As a chemical composition thereof, Al2O3.nSiO2.mH2O is exemplified (n and m are the numbers of coordination of silicon dioxide and water to aluminum oxide, respectively). That in which water is coordinated is preferable. As a synthetic magnesium silicate, those having a silicon dioxide content of 55 to 70% by weight and a magnesium oxide content of 5 to 20% by weight are preferable. As chemical composition thereof, MgO.xSiO2.yH2O is exemplified (x and y are the numbers of coordination of silicon dioxide and water to magnesium oxide, respectively). That in which water is coordinated is particularly preferable.
The temperature at which a crude polyoxyalkylene polyol is allowed to contact with a solid acid may be a temperature near room temperature. However, when shortening of the treatment time and improvement in ability for removing a catalyst are taken into consideration, the contact temperature is preferably in the range from 50 to 150xc2x0 C. It is more preferably from 60 to 140xc2x0 C., and preferably still from 70 to 130xc2x0 C. When the molecular weight of a polyoxyalkylene polyol is larger, contact at a temperature of 50xc2x0 C. or more is preferable due to increased viscosity. When over 150xc2x0 C., a crude polyoxyalkylene polyol tends to be colored.
As the method for allowing a crude polyoxyalkylene polyol to contact with a solid acid, two methods, a batch-wise method and a continuous method are listed. The batch-wise method is, for example, a method in which a solid acid is added to a crude polyoxyalkylene polyol charged into a reaction apparatus, and they are mixed by stirring. For the purpose of preventing coloring and degradation of a polyoxyalkylene polyol, it is preferable to conduct mixing by stirring in the presence of an inert gas. The amount used of a solid acid is from 0.01 to 2% by weight based on a crude polyoxyalkylene polyol. It is preferably from 0.05 to 1.5% by weight, and preferably still from 0.1 to 1% by weight. The contact time is preferably from 1 to 6 hours under the above-described temperature condition though it depends on the scale. The continuous method is a method in which a crude polyoxyalkylene polyol is passed though a column charged with a solid acid. The superficial velocity is preferably from about 0.1 to 3 (1/hr) though it depends on the scale. After contact with a solid acid, a polyoxyalkylene polyol is recovered by an ordinary method such as filtration, centrifugal separation and the like.
For further improving ability of a solid acid to adsorb a catalyst, it is preferable that, when a crude polyoxyalkylene polyol is allowed to contact with a solid acid, water in an amount of 0.1 to 10% by weight is allowed to coexist with the crude polyoxyalkylene polyol. This amount is more preferably from 1 to 8% by weight, and preferably still from 2 to 7% by weight. For coexistence of a solid acid with water, these may be advantageously added into a polyol. The order for addition of these is not restricted. The temperature when water is added to a crude polyoxyalkylene polyol is preferably from 50 to 150xc2x0 C. In the case of addition of water, a crude polyoxyalkylene polyol and a solid acid are mixed by stirring, for example, at a temperature of 90xc2x0 C. for 5 hours, then, pressure-reduced dehydration operation is conducted, for example, under conditions of a temperature of 110xc2x0 C. and a pressure of 1.33 kPa, to remove water.
For preventing degradation of a polyoxyalkylene polyol, an antioxidant is preferably added to the polyoxyalkylene polyol. The antioxidant may be used alone or in combination with two or more. Examples of the antioxidant include tert-butylhydroxytoluene (BHT), pentaerythrityl-tetrakis-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate, 7 ethylhexylphosphite, 4,4xe2x80x2-bis-xcex1,xcex1xe2x80x2-dimethylbenzyldiphenylamine, 2-tert-butyl-4-ethylphenyl, 2,6-di-tert-butyl-4-ethylphenol and the like. The amount added of an antioxidant is from 100 to 2000 ppm based on a polyoxyalkylene polyol.
Further, when a purified polyoxyalkylene polyol and a polyisocyanate compound are reacted to produce an isocyanate group-ended prepolymer, an acid can also be added to the polyoxyalkylene polyol obtained by the above-described method for the purpose of improving storage stability of the prepolymer. As the acid, inorganic acids and organic acids are listed. Examples of inorganic acid include phosphoric acid, phosphorous acid, hypophosphorous acid, pyrophosphoric acid, and aqueous solutions thereof. Examples of the organic acid include formic acid, oxalic acid, succinic acid, acetic acid, maleic acid, benzoic acid, p-toluenesulfonic acid, and aqueous solutions thereof. Phosphoric acid and maleic acid are preferable, and it is recommendable to use them in the form of a solution. The amount added of an acid is from 1 to 25 ppm based on a polyoxyalkylene polyol. It is preferably from 1 to 20 ppm, and preferably still from 1 to 15 ppm. An acid is preferably used in the above-described addition amount range and simultaneously in the range wherein pH of a polyoxyalkylene polyol is not lower than 5 and the acid value is not over 8 mg KOH/g.
Further, the concentration of a peroxide in a polyoxyalkylene polyol obtained by the above-described operation is preferably 0.28 mmol/kg or less. It is preferably still 0.2 mmol/kg or less, most preferably 0.15 mmol/kg or less. If the concentration of a peroxide is over 0.28 mmol/kg, when a tin-based catalyst is used in reaction with a polyisocyanate compound, the activity of the tin-based catalyst lowers because of the peroxide and therefore, molding property and mechanical property of a polyurethane decrease.
A purified polyoxyalkylene polyol obtained as described above has the following properties, namely, (1) OHV in the range from 2 to 200 mg KOH/g, (2) total unsaturation degree (hereinafter, referred to as Cxe2x95x90C) in the range of 0.07 meq./g or less, (3) a head-to-tail bond selectivity (hereinafter, referred to as Hxe2x80x94T selectivity) of an oxypropylene group of 95 mol % or more, and (4) a catalyst-remaining amount of 150 ppm or less (hereinafter, these are called four conditions of a polyoxyalkylene polyol of the present invention).
OHV of a polyoxyalkylene polyol is preferably from 9 to 120 mg KOH/g, and preferably still from 11 to 60 mg KOH/g. When addition-polymerization of an epoxide compound, particularly propylene oxide is conducted until OHV becomes under 2 mg KOH/g, the reaction time of a polyoxyalkylene polyol becomes too long. When OHV is over 200 mg KOH/g, the molecular weight of a polyoxyalkylene polyol decreases and the flexibility of the resulting polyurethane lowers.
Cxe2x95x90C in a polyoxyalkylene polyol is mainly an index of the amount of a monool having an unsaturated group at the molecular end produced by a sub-reaction of propylene oxide. Cxe2x95x90C is not more than 0.07 meq./g. An amount greater than this is not preferable since the mechanical property of a polyurethane resin of a flexible polyurethane foam, elastomer, sealing material and the like lowers. From the standpoint of such a condition, Cxe2x95x90C is preferably 0.05 meq./g or less, and preferably still 0.03 meq./g or less. Depending on the usage of a polyurethane resin, Cxe2x95x90C of a polyoxyalkylene polyol is preferably 0. However, 0 is not necessarily preferable industrially, since then reaction conditions such as reaction temperature, pressure and the like should be extremely loose leading to too long a reaction time. Under such conditions, the lower limit of Cxe2x95x90C is preferably about 0.001 meq./g.
When the Hxe2x80x94T bond selectivity based on an oxypropylene group by propylene oxide addition polymerization decreases under 95% in a polyoxyalkylene polyol having such a low Cxe2x95x90C, there occur problems in that the viscosity of the polyoxyalkylene polyol increases, molding property of a flexible polyurethane foam deteriorates due to poor compatibility with an auxiliary agent such as a silicone surfactant and the like, as well as other disadvantages. Due to an increase in viscosity in raising the molecular weight of a polyoxyalkylene polyol, the viscosity of a prepolymer obtained by reaction with a polyisocyanate compound also increases and therefore, workability lowers. From the standpoint of such a condition, the Hxe2x80x94T bond selectivity is 95 mol % or more, and preferably still 96% or more.
The remaining amount of the catalyst in a polyoxyalkylene polyol is 150 ppm or less. When the catalyst-remaining amount is over 150 ppm, an isocyanate group-ended prepolymer obtained by reacting a polyoxyalkylene polyol with a polyisocyanate compound manifests change in viscosity by time. The catalyst-remaining amount is preferably 90 ppm or less, and preferably still 50 ppm or less. It is recommendable that the lower limit of the catalyst-remaining amount is as low as possible. Usually, the lower limit can be lowered to about 1 ppm according to the above-described purification method.
 less than Production Method of Polymer-dispersed Polyol greater than 
Herein, a method for producing a polymer-dispersed polyol of the present invention will be described.
As methods for producing a polymer-dispersed polyol, there are listed a method (hereinafter, referred to as Method I) in which an ethylenically-unsaturated monomer is polymerized by continuous operation or batch-wise operation in a polyoxyalkylene polyol to disperse a polymer particle in the polyol, and a method (hereinafter, referred to as Method II) in which a polymer solution previously polymerized in a solvent and the like is added to a polyoxyalkylene polyol, then, the solvent is removed, to disperse a polymer particle in the polyol. In view of the productivity of a polymer-dispersed polyol, Method I, in particular the continuous operation thereof is preferable. Method I will be first described.
The polyoxyalkylene polyol used in producing a polymer-dispersed polyol in the present invention is a polyoxyalkylene polyol satisfying the above-described four conditions (1) through (4). OHV in a polyoxyalkylene polyol is preferably in the range from 10 to 150 mg KOH/g. Preferably still, it is in the range from 15 to 100 mg KOH/g. The etlhylenically-unsaturated monomer for forming a polymer particle is a compound having at least one ethylenically-unsaturated group which can be polymerized.
Examples of such an etlylenically-unsaturated monomer include cyano group-containing monomers such as acrylonitrile, methacrylonitrile and the like; methacrylate-type monomers such as methyl acrylate, butyl acrylate, stcaryl acrylate, hydroxyethyl acrylate, dimethylaminoethyl acrylate, dimethylaminopropyl methacrylatc and the like; carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and the like; acid anhydride group-containing monomers such as maleic anhydride, itaconic anhydride and the like; hydrocarbon-based monomers such as butadiene, isoprene, 1,4-pentadiene and the like; aromatic hydrocarbon-based monomers such as styrene, (-methylstyrene, phenylstyrene, chlorostyrene and the like; halogen-containing monomers such as vinyl chloride, vinylidene chloride and the like; vinyl ethers such as vinyl ethyl ether, vinyl butyl ether and the like; vinyl ketones such as vinyl ethyl ketone and the like; vinyl esters such as vinyl acetate and the like; acrylarnides such as acrylamide, N,N-dimethylacrylamide, N-isopropylacrylamide, N,N-dimethylaminopropylacrylamide, metliylenebisacrylamide and the like; and methacrylamides such as N,N-dimethylmethacryloylamide and the like. These may be used alone or in combinations of two or more.
Of them, preferable are ethylenically-unsaturated monomers containing at least one compound selected from acrylonitrile, styrene, acrylamide and methyl methacrylate.
The dispersion concentration of a polymer particle depends on the amount used of an ethylenically unsaturated monomer and the conversion thereof. The conversion of an ethylenically-unsaturated monomer is 70% by weight or more though it depends on the production condition of a polymer-dispersed polyol. It is preferably 80% by weight or more. The amount used of an ethylenically-unsaturated monomer is determined in view of conversion thereof. Specifically, it is from 5 to 86 parts by weight based on 100 parts by weight of the above-described polyoxyalkylene polyol which is a dispersing medium. It is preferably from to 8 to 70 parts by weight, and preferably still from 9 to 52 parts by weight. Thus, a polymer-dispersed polyol is obtained in which the concentration of a dispersed polymer particle is from 5 to 60% by weight based on the total amount of a polyoxyalkylene polyol which is a dispersion medium and the polymer particle. It is preferably from 10 to 50% by weight, and preferably still from 12 to 45% by weight. When the concentration of the polymer particle is less than 5% by weight, no sufficient improving effect is obtained by use of the polymer-dispersed polyol such as hardness of a polyurethane, ventilation property of a polyurethane foam, and the like. When the concentration of the polymer particle is over 60% by weight, an increase in viscosity of the resulting polymer-dispersed polyol is remarkable, and dispersion stability also deteriorates.
The average particle size of a polymer particle to be dispersed in a polyoxyalkylene polyol is preferably from 0.01 to 10 xcexcm. It is preferably still from 0.05 to 7 xcexcm, most preferably from 0.08 to 5 xcexcm. When the average particle size is less than 0.01 xcexcm, the viscosity of a polymer-dispersed polyol increases. On the other hand, when the average particle size is more than 10 xcexcm, the dispersion stability of a polymer deteriorates.
In polymerization of an ethylenically unsaturated monomer, a radical polymerization initiator is used. Specifically, there are listed azo compounds such as 2,2xe2x80x2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2xe2x80x2-azobis(2-methylbutylnitrile), 2,2xe2x80x2-azobis(isobutyronitrile) and the like, peroxide such as benzoyl peroxide, t-butyl peroxide, di-t-butyl peroxide and the like, peroxy disulfide and the like. The amount used of a polymerization initiator is usually from 0.1 to 10% by weight based on an ethylenically unsaturated monomer. It is preferably from 0.5 to 5% by weight.
It is preferable to use a chain transfer agent together with a radical polymerization initiator. Examples of the chain transfer agent include alcohols such as methanol, ethanol, propanol, isopropanol, pentanol and the like; mercaptans; halogenated hydrocarbons; aliphatic amines such as triethylamnine, tripropylamine, tributylamine, N,N-diethylethanolamine and the like; morpholines such as N-methylmorpholine, N-ethylmorpholine and the like; sodium methallylsulfonate, sodium allylsulfonate, toluene, xylene, acetonitrile, hexane, heptane, dioxane, ethylene glycol dimethyl ether, N,N-dimethylformaldehyde and the like. Among these, triethylamine and a mixture of triethylamine and isopropanol are preferable. The amount used of a chain transfer agent is preferably from 0.01 to 10% by weight based on the total weight of a polyoxyalkylene polyol and an etliylenically unsaturated monomer. It is preferably still from 0.05 to 5% by weight.
Further, for the purpose of dispersing a polymer particle, polymerization can also be conducted in the presence of a dispersion stabilizer. As this dispersion stabilizer, there are listed a polyester polyol containing a carbon-carbon unsaturated bond, modified polyols having an acryl group, methacryl group, allyl group and the like on the molecular end, and the like, as described in Japanese Patent Publication (JP-B) No. Sho-49-46556. Also, a polyoxyalkylene polyol having high molecular weight and a polyester polyol having substantially no carbon-carbon unsaturated bond can be used as a dispersion stabilizer.
An ethylenically unsaturated monomer, polymerization initiator, and if necessary, a chain transfer agent, dispersion stabilizer and the like are added to the above-described polyoxyalkylene polyol, and polymerization reaction is conducted. The polymerization temperature of an ethylenically unsaturated monomer is determined according to the kind of a radical polymerization initiator used. Usually, it is polymerized at a temperature not less than the decomposition temperature of the initiator. It is preferably from 40 to 200xc2x0 C., and preferably still from 90 to 150xc2x0 C. The polymerization reaction can also be conducted under increased pressure and atmospheric pressure. While the polymerization reaction can also be conducted without solvents, it can also be conducted in the presence of at least one solvent selected from water and organic solvents. Examples of the organic solvent include toluene, xylene, acetonitrile, hexane, heptane, dioxane, ethylene glycol dimethyl ether, N,N-dimethylformamide, methanol, ethanol, butanol, isopropanol and the like.
After completion of the polymerization reaction, the resulting polymer-dispersed polyol can be used without treatment as a raw material of a polyurethane. However, this polyol is preferably used after removal by distillation under reduced pressure of an unreacted ethylenically unsaturated monomer, a decomposition product of a polymerization initiator, a chain transfer agent, a solvent and the like. The condition for the pressure-reduced distillation-off operation is not particularly restricted, and it is usually conducted using an apparatus such as a forced thin film evaporation apparatus and the like under conditions of a temperature of 70 to 150xc2x0 C. and a pressure of 1.33 kPa or less.
Herein, a method in which a polymer solution previously polymerized in a solvent and the like is added to a polyoxyalkylene polyol, then, the solvent is removed, to disperse a polymer particle in the polyol (Method II) will be described. An ethylenically unsaturated monomer, polymerization initiator and the like for forming a polymer particle, with compounds as described above are used. The polymerization temperature is usually from 40 to 200xc2x0 C. though this depends on chemical and physical properties of the polymerization initiator and ethylenically unsaturated monomer used. It is preferably in the range from 90 to 150xc2x0 C. As the solvent to be used for polymerization, at least one solvent is selected from the above-described organic solvents and water, though this depends on the chemical and physical properties of the polymerization initiator and ethylenically unsaturated monomer used. The amounts used of the polymerization initiator and ethylenically unsaturated monomer are not particularly restricted, and usually from 0.01 to 10% by weight and 3 to 60% by weight, respectively, based on the solvent. In polymerization of monomers, the chain transfer agent as described above may be advantageously used.
After a polymer particle is formed in a solvent, the resulting polymer solution and the above-described polyoxyalkylene polyol are mixed. The mixing condition is not particularly restricted, and the mixing is usually conducted at a temperature from 15 to 150xc2x0 C. It is preferably in the range from 20 to 120xc2x0 C. The mixing is conducted for about 0.5 to 5 hours by stirring. Then, removal operation of a solvent is conducted. A heat pressure-reducing operation is carried out usually under conditions of a temperature from 70 to 150xc2x0 C. and a pressure of 1.33 kPa or less for about 1 to 6 hours to remove a solvent, though the conditions depend on chemical and physical properties of a solvent and polymer used. In this procedure, a pressure-reducing operation can also be conducted while passing an inert gas through a polyoxyalkylene polyol for quick removal of a solvent.
The average particle size of a polymer contained in polymer-dispersed polyol exerts influence on the dispersion stability and the viscosity of the polymer-dispersed polyol. From such standpoints, the average particle size of a polymer is suitably from 0.01 to 10 xcexcm. Such a particle size can be obtained by suitably controlling kinds and amounts used of the above-described chain transfer agent, dispersion stabilizer, solvent and the like, weight composition of an ethylenically unsaturated monomer, and the like, in addition to properties of a polyoxyalkylene polyol which is a dispersion medium.
 less than Production Method of Isocyanate Group-ended Prepolymer (1) greater than 
A method for producing an isocyanate group-ended prepolymer using as a raw material a polyoxyalkylene polyol will be described. The isocyanate group-ended prepolymer is produced by reacting a polyol with a polyisocyanate compound. The polyol used in the present invention is a polyoxyalkylene polyol satisfying the above-described four conditions (1) through (4) or the above-described polymer-dispersed polyol derived from this polyoxyalkylene polyol.
First, a method using a polyoxyalkylene polyol as the polyol will be described. This polyol is a polyoxyalkylene polyol satisfying the above-described four conditions (1) through (4). Of them, those having a catalyst-remaining amount of 50 ppm or less are preferable. Further, CPR (Controlled Polymerization Rate: index showing the amount of basic substances in polyol) of a polyoxyalkylene polyol is preferably 3 or less. It is preferably still 1 or less, most preferably 0. When the CPR is over 3, the storage stability of an isocyanate group-ended prepolymer lowers.
The catalyst-remaining amount in an isocyanate group-ended prepolymer is preferably 120 ppm or less. It is preferablystill 70 ppm or less, most preferably 20 ppm or less. The catalyst-remaining amount in an isocyanate group-ended prepolymer is attained by controlling the catalyst-remaining amount in a polyoxyalkylene polyol to 150 ppm or less. When the catalyst-remaining amount in an isocyanate group-ended prepolymer is over 120 ppm, change in the viscosity of the prepolymer by time increases. The lower limit of the catalyst-remaining amount may advantageously be as low as possible. Usually, according the above-described method for purifying a polyoxyalkylene polyol, a catalyst can be removed to give a remaining amount of about 1 ppm, the catalyst-remaining amount in an isocyanate group-ended prepolymer can be reduced to about 1 ppm.
As the polyisocyanate compound used in the present invention, aromatic, aliphatic and alicyclic compounds and the like having two or more isocyanate groups in one molecule can be used. Examples of the aromatic isocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, isomer mixtures of these polyisocyanates in an 80:20 ratio by weight (TDI-80/20) and an 63:35 ratio by weight (TDI-65/35), 4,4xe2x80x2-diphenylmethane diisocyanate, 2,4xe2x80x2-diphenylmethane diisocyanate, 2,2xe2x80x2-diphenylmethane diisocyanate, any isomer mixtures of diphenylmethane diisocyanates, toluylene diisocyanate, xylylene diisocyanate, xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetramethylxylylene diisocyanate, p-phenylene diisocyanate, naphthalene diisocyanate and the like, and compounds obtained by hydrogenation of these polyisocyanates.
Examples of the aliphatic isocyanate include ethylene diisocyanate, 1,4-butane diisocyanate, 1,6-hexane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, dodecamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate and the like. Examples of the alicyclic isocyanate include isophorone diisocyanate, norbornene diisocyanate, dicyclohexyl methane diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate and the like.
Further, modified isocyanates such as carbodiimide modified substances, buret modified substances, isocyanurate modified substances and the like of the above-described polyisocyanate can also be used. There can be also used isocyanate compounds obtained by modification of a polyisocyanate and modified polyisocyanate with the above-described active hydrogen compounds, polyols having an average number molecular weight of 100 to 6000 g/mol, and monools such as methanol, ethanol, n-propanol, isopropanol, butanol, allyl alcohol and the like alone or a mixture thereof. Further, polyols having a number-average molecular weight of 100 to 3000 g/mol obtained by addition-polymerization of an epoxide compound to a monool may also be used. The above-described polyisocyanate and modified polyisocyanate can also be mixed for use. The preferable mixing ratio is in the range from 5:95 to 95:5 in terms of ratio by weight of the polyisocyanate to the modified polyisocyanate, preferably still in the range from 10:90 to 90:10, most preferably in the range from 30:70 to 70:30.
Among the above-described polyisocyanates, preferable are 2,4-tolylene diisocyanate (hereinafter, referred to as 2,4-TDI), 2,6-tolylene diisocyanate (hereinafter, referred to as 2,6-TDI), isomer mixtures of these polyisocyanates in 80:20 ratio by weight (TDI-80/20) and 63:35 ratio by weight (TDI-65/35), hydrogenated TDI-80/20, hydrogenated TDI-65/35, 4,4xe2x80x2-diphenylmethane diisocyanate (hereinafter, referred to as MDI), hydrogenated MDI, p-phenylene diisocyanate, xylylene diisocyanate (hereinafter, referred to as XDI), hydrogenated XDI, hexamethylene diisocyanate (hereinafter, referred to as HDI), isophorone diisocyanate (hereinafter, referred to as IPDI), norbornene diisocyanate (hereinafter, referred to as NBDI), and dicyclohexylmethane diisocyanate (hereinafter, referred to as DCHMDI).
Further, preferable are buret modified substances, isocyanurate modified substances, and glycerin modified substances, trimethylolpropane modified substances of these polyisocyanates, and polyisocyanate modified substances modified with a polyol obtained by addition-polymerization of propylene oxide, ethylene oxide and the like to glycerine or trimethylolpropane. Particularly preferable are TDIs, MDIs, XDIs, HDIs, IPDIs and NBDIs, isocyanurate modified substances, buret modified substances and polyol modified substance of these polyisocyanates, and mixtures thereof.
An NCO index which is an equivalent ratio of an isocyanate group to an active hydrogen group in a polyol in producing an isocyanate group-ended prepolymer is in the range from 1.3 to 10. It is preferably from 1.4 to 9, preferably still from 1.5 to 8. The isocyanate group content (hereinafter, referred to as NCO %) in an isocyanate group-ended prepolymer is from 0.3 to 30% by weight. It is preferably from 0.5 to 25% by weight, preferably still from 0.8 to 15% by weight, most preferably from 1 to 10% by weight. In an isocyanate group-ended prepolymer used in a one-pack type curing composition obtained by reacting with water in air, NCO % is designed at a lower value within the above-described range. While, in an isocyanate group-ended prepolymer used in a two-pack type curing composition obtained by using as a curing agent glycols such as 1,4-butanediol, dipropylene glycol, polyoxyalkylene polyol and the like, or polyamine compounds such as 3,3xe2x80x2-dichloro-4,4xe2x80x2-diaminodiphenylmethane, diethyldiaminotoluene and the like, NCO % is designed at a higher value as compared with the one-pack composition.
The Hxe2x80x94T bond selectivity of the main chain in an isocyanate group-ended prepolymer produced in the present invention is 95 mol % or more. This is attained by controlling the Hxe2x80x94T bond selectivity of an oxypropylene group by propylene oxide addition-polymerization of a raw material, poloyoxyalkylene polyol to 95 mol % or more. By controlling the Hxe2x80x94T bond selectivity of the main chain of an isocyanate group-ended prepolymer to 95 mol % or more, low viscosity can be attained even if the molecular weight is raised. The Hxe2x80x94T bond selectivity of a prepolymer is preferably 96% or more.
As the catalyst in prepolymer reaction, known catalysts used in producing a polyurethane, such as amine compounds, organic metal compounds and the like, can be used. When the molecular weight of a polyoxyalkylene polyol is lower, namely, when OHV is high, there are cases wherein no catalyst need be used. Examples of the amine compound include triethylamine, tripropylamine, tributylamine, N,N,Nxe2x80x2,Nxe2x80x2-tetramethylhexamethylenediamine, N-metlylmorpholine, N-ethylmorpholine, dimethylcyclohexylamine, bis[2-(dimethylamino)ethyl] ether, triethylenediamine, and salts of triethylenediamine, and the like. Examples of the organic metal compound include tin acetate, tin octylate, tin oleate, tin laurate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, lead octanoate, lead naphthenate, nickel naphthenate, cobalt naphthenate and the like. These catalysts can be used alone, and further, can be optionally used in mixtures of two or more. Of these catalysts, organometal-based catalysts are particularly preferable. The amount used thereof is from 0.0001 to 2.0 parts by weight based on 100 parts by weight of a polyoxyalkylene polyol. It is preferably from 0.001 to 1.0 parts by weight.
The temperature when a prepolymer is produced is preferably from 50 to 120xc2x0 C. It is preferably still from 60 to 110xc2x0 C., particularly preferably from 70 to 100xc2x0 C. When a polyol is reacted with a polyisocyanate compound, the reaction is preferably conducted in the presence of an inert gas for avoiding contact with water in air. As the inert gas, nitrogen, helium and the like are listed. Nitrogen is preferable. The reaction is conducted under a nitrogen atmosphere for 2 to 10 hours by stirring.
When an isocyanate group-ended urethane prepolymer is produced, an organic solvent which is inactive with the polyisocyanate and polyol may be used before and after the reaction or during reaction. The amount of an organic solvent in is preferably 100% by weight or less based on the total amount of the polyol and polyisocyanate. It is preferably still 60% by weight or less, most preferably 40% by weight or less. As such an organic solvent, aromatic, aliphatic, alicyclic, ketone-based, ester-based and ester ether-based solvents are listed. Examples thereof include toluene, xylenes, hexanes, acetone, cyclohexane, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylcellosolve acetate, butylcellosolve acetate and the like.
Herein, a method for producing an isocyanate group-ended prepolymer having a free isocyanate compound content of 1% by weight or less will be described. An NCO % of the isocyanate group-ended prepolymer having a free isocyanate compound content of 1% by weight or less is from 0.3 to 30% by weight. It is preferably from 0.5 to 25% by weight, and preferably still from 1 to 15% by weight. The free isocyanate compound content in an isocyanate group-ended prepolymer is preferably 0.8% by weight or less. It is preferably still 0.5% by weight or less, and most preferably 0.1% by weight or less. When the free isocyanate compound content exceeds 1% by weight, hysteresis of polyurethane increases.
For controlling the free isocyanate compound content in in an isocyanate group-ended prepolymer to 1% by weight or less, pressure-reducing treatment of the above-described isocyanate group-ended prepolymer is conducted under conditions of specific temperature and specific pressure. An isocyanate group-ended prepolymer which is a raw material of the isocyanate group-ended prepolymer having a free isocyanate compound content of 1% by weight or less is produced by the above-described method. Pressure-reducing treatment is an important process for suppressing production of a dimer of an unreacted isocyanate compound in the pressure-reducing treatment process. The temperature in the pressure-reducing operation is from 70 to 180xc2x0 C. It is preferably from 80 to 170xc2x0 C., and preferably still from 85 to 160xc2x0 C. When the temperature is lower than 70xc2x0 C., the time for removing an unreacted isocyanate compound is elongated. When the temperature is over 180xc2x0 C., the viscosity of a prepolymer increases in the pressure-reducing process. The pressure is 665 Pa or less. It is preferably 266 Pa or less, and preferably still 133 Pa or less. It is most preferably 13.3 Pa or less. When the pressure is over 665 Pa, the time for removing an unreacted polyisocyanate compound is elongated, and the viscosity of a prepolymer increases in the pressure-reducing treatment process.
The pressure-reducing treatment is preferably a thin in layer evaporation method. An evaporation vessel of a forced cycling stirring film type, falling film molecule evaporator or the like can be used (see, Kagaku Kogaku Handbook, Revised 5 Edition, ed. Kagaku Kogaku Institute, MARUZEN, 1998). As such an apparatus, for example, a Smith type film evaporator (manufactured by Shinko Pantech K.K.: Wipelen, Exceva) or a Contro type film evaporator [manufactured by Hitachi Ltd., trade name: Sunvey type film evaporator] is listed. A polyisocyanate compound recovered from a prepolymer by pressure-reducing treatment can be used in prepolymer reaction again. In use, a polyisocyanate compound containing impurities such as a dimer and the like is preferable.
To an isocyanate group-ended prepolymer produced as described above, a catalyst for curing, silicone-based coupling agent, a filler, a plasticizer, a pigment, a reinforcing agent, a flame retardant, a stabilizer, a defoaming agent and the like can be added according to the object. Further, for the purpose of suppressing change in viscosity by time of a prepolymer, an inorganic acid, organic acid or the like may be added to the prepolymer. As the inorganic acid, phosphoric acid, pyrophosphoric acid and the like are listed. As the organic acid, for example, adipic acid, 2-ethylhexanoic acid, oleic acid and the like are listed. These acids can be used alone, and further, can also be used in combinations of two or more. The amount used thereof is preferably from 0.0001 to 3 parts by weight based on 100 parts by weight of an isocyanate group-ended prepolymer. It is preferably still from 0.003 to 1 part by weight.
 less than Production Method of Isocyanate Group-ended Prepolymer (2) greater than 
Next, a method using a polymer-dispersed polyol as the polyol will be described. An isocyanate group-ended prepolymer obtained by using a polymer-dispersed polyol is basically produced by the same method as the above-described method using a polyoxyalkylene polyol. Regarding a polyisocyanate compound, addition auxiliaries and the like, those as described above are used. Namely, instead of a polyoxyalkylene polyol, a polymer-dispersed polyol is used. As the polymer-dispersed polyol, those obtained in the method for producing a polymer-dispersed polyol of the above-described present invention are used. In view of the viscosity of an isocyanate group-ended prepolymer, among polymer-dispersed polyols of the present invention, those having a polymer concentration of 5 to 30% by weight are preferable. An NCO % of an isocyanate group-ended prepolymer is from 0.3 to 30% by weight, preferably from 1 to 15% by weight.
 less than Production Method of Polyurethane Resin (1) greater than 
A method for producing a polyurethane resin using as a raw material an isocyanate group-ended prepolymer will be described. A polyurethane resin is produced by reacting a prepolymer containing an isocyanate group-ended prepolymer produced by the above-described method with a chain extender. The isocyanate group-ended prepolymer and chain extender are reacted in amounts so that the isocyanate index is from 0.6 to 1.5. It is preferably from 0.8 to 1.3, and preferably still from 0.9 to 1.2. The resulting polyurethane resin can be used mainly in the fields of a polyurethane elastomer, polyurethane urea elastomer, paint, adhesive and the like.
The prepolymer preferably contains an isocyanate group-ended prepolymer produced by the above-described production method in an amount of at least 60% by weight. Further preferable content is at least 70% by weight. Most preferable is an isocyanate group-ended prepolymer separately produced by the above-described method. As preferable embodiments of an isocyanate group-ended prepolymer obtained by another production method than that of the present invention, there is, for example, an isocyanate group-ended prepolymer containing as a polyol component polytetramethylene glycol, polyoxyethylene adipate, and polycaprolactone polyol exemplified in Japanese Patent Application Publication (JP-B) No. Hei-6-13593. When the content of an isocyanate group-ended prepolymer obtained by using as a raw material a polyoxyalkylene polyol obtained by the method of the present invention is less than 60% by weight, the viscosity of the prepolymer increases and workability decreases.
The chain extender is a compound containing in one molecule two or more active hydrogen groups which can be reacted with an isocyanate group. For example, at least one active hydrogen group-containing a compound of a polyol compound or polyamine compound is listed. Examples of the polyol compound include divalent alcohols such as ethylene glycol, propylene glycol, dipropylene glycol, diethylene glycol, triethylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol and the like; trivalent alcohols such as glycerine, trimethylolpropane and the like; cyclohexylenes such as 1,4-cyclohexanediol, spirohexanediol and the like; and compounds containing a spiro ring and methylene chain and various bonds such as an ether bond, ester bond and the like for connecting the spiro ring and methylene chain.
Further, those containing various substituents as derivatives thereof can be used. Further, as the aromatic alcohols, there can be used compounds such as hydroquinone, resorcin, bishydroxyethylene terephthalate and the like, and polyols obtained by adding at least one alkylene oxide selected from ethylene oxide and propylene oxide in an amount of 1 to 4 mol per hydroxyl group of these compounds.
As the polyamine compound, there can be used tolylenediamine, 3,5-diethyl-2,4-diaminotoluene, 3,5-diethyl-2,6-diaminotoluene, diphenylmethanediamine, and mixtures of their isomers, and aromatic diamines such as ni-phenylenediamine, 3,3xe2x80x2-dichloro-4,4xe2x80x2-diaminodiphenylmethane. Further, there can be used conventionally known polyamine compounds of alicyclic diamines such as isophoronediamine, norbornenediamine and the like, linear aliphatic diamines such as ethylenediamine and the like, alkyldihydrazides such as carbodihydrazide, dihydrazide adipate and the like, or derivatives thereof, and the like. Further, amino group-containing polyols obtained by adding an alkylene oxide to these active hydrogen compounds by a conventionally known method can be used as the chain extender. These polyols and polygamies can be mixed in any ratio to be used as the chain extender.
Of the above-described compounds, preferable are ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, 1,4-cyclohexanediol, glycerine, trimethylolpropane, 3,5-diethyl-2,4-diaminotoluene, 3,5-diethyl-2,6-diaminotoluene, 3,3xe2x80x2-dichloro-4,4xe2x80x2-diaminodiphenylmethane, isophoronediamine, norbornenediamine, and polyols obtained by addition-polymerization of an alkylene oxide to these compounds.
The isocyanate group-ended prepolymer and chain extender as described above are previously controlled to a given temperature, for example, from 30 to 150xc2x0 C., and pressure-reduced defoaming treatment is conducted. Then, both components are mixed by quick stirring, and injected in a mold heated to a given temperature, for example, from 40 to 140xc2x0 C., to produce a molded product (polyurethane resin). In this procedure, a catalyst for curing, inorganic acid, organic acid, silicone-based coupling agent, filler, plasticizer, pigment, reinforcing agent, flame retardant, stabilizer, defoaming agent and the like can be added according to the use object of a polyurethane resin.
For the purpose of suppressing change in viscosity by time of a prepolymer, an inorganic acid or organic acid may be added to the prepolymer. As the inorganic acid, phosphoric acid is preferable. As the organic acid, for example, adipic acid, 2-ethylhexanoic acid, oleic acid and the like can be used. These acids can be used alone, and further, can also be used in combinations of two or more. The amount used thereof is preferably from 0.001 to 10.0 parts by weight based on 100 parts by weight of the above-described isocyanate group-ended prepolymer. It is preferably from 0.003 to 5.0 parts by weight.
By reacting a prepolymer containing as the main component an isocyanate group-ended prepolymer of the present invention with a chain extender containing an active hydrogen group as described above, a polyurethane resin is produced. In addition to this method, a one shot method can also be applied in which a polyol containing at least 60% by weight of a polyoxyalkylene polyol of the present invention, a polyisocyanate, and a chain extender are simultaneously mixed and molded.
 less than Production Method of Polyurethane Resin (2) greater than 
Next, a method for producing a polyurethane resin using as a curing agent a polyoxyalkylene polyol obtained by the above-described production method will be described. This polyurethane resin is produced by reacting a polyoxyalkylene polyol obtained by the above-described production method with an isocyanate group-ended prepolymer. Usually, a polyurethane resin obtained by such a method is used for waterproofing and sealing uses. A polyoxyalkylene polyol used as a curing agent satisfies the conditions (1) through (4) explained in the column of the production method of a polyoxyalkylene polyol. Of these, OHV is preferable from 8 to 100 mg KOH/g. Preferable still, is a polyoxyalkylene polyol having an OHV from 10 to 50 mg KOH/g.
Auxiliaries such as an urethane-forming catalyst, plasticizer, ultraviolet absorber, antioxidant, filler, reinforcing agent, flame retardant, defoaming agent, pigment, silicone-based coupling agent and the like may be previously added to a polyoxyalkylene polyol. As auxiliaries, conventionally known compounds can be used. The total amount added of the auxiliaries is from 10 to 800 parts by weight based on 100 parts by weight of a polyoxyalkylene polyol. It is preferably from 20 to 700 parts by weight. In the case of the by polyoxyalkylene polyol obtained by the above-described method, polyoxyalkylene polyols having different molecular weights (OHV), numbers of functional groups, and oxypropylene group contents may be mixed in any ratio.
As the silicone-based coupling agent, there are listed, for example, xcex-aminopropyltrimetthoxysilane, xcex-mercaptopropyltrimethoxysilane, xcex-glycidoxypropyltrimethoxysilane and the like. The amount used thereof is preferably from 0.01 to 8 parts by weight based on 100 parts by weight of a polyoxyalkylene polyol. It is preferably from 0.03 to 5 parts by weight. The polyamine compound as described above may be added to a polyoxyallylene polyol.
For improving the dispersion stability of a polyoxyalkylene polyol and the above-described auxiliaries, mixing by stirring is conducted sufficiently. The mixing by stirring is preferably conducted according to a kneading mode using an apparatus equipped with a single or twin screw. An isocyanate group-ended prepolymer used as the main agent is preferably an isocyanate group-ended prepolymer produced by the above-described method. An isocyanate group-ended prepolymer produced by the other method may be used. In this case, that containing an isocyanate group-ended prepolymer produced by the above-described method in an amount of at least 60% by weight is preferable. Further preferable content is 70% by weight.
An isocyanate group-ended prepolymer which is the main agent and a polyoxyalkylene polyol which is the curing agent are sufficiently mixed by stirring, and the resulting mixed solution is cured at a temperature in the range from 10 to 50xc2x0 C. The curing time is usually from 1 to 7 days though this depends on the amount of catalyst added to a curing agent. The polyoxyalkylene polyol and isocyanate group-ended prepolymer are reacted in amounts so that the isocyanate index is from 0.8 to 1.3. It is preferably from 0.85 to 1.2, further preferably from 0.9 to 1.1.
 less than Production Method of Flexible Polyurethane Foam greater than 
Finally, a method for producing a flexible polyurethane foam will be described. The whole density of a flexible polyurethane foam produced by the present invention is preferably from 20 kg/m3 to 60 kg/m3. It is preferably still from 25 kg/m3 to 55 kg/m3, most preferably from 27 kg/m3 to 50 kg/m3. The elongation of a foam which is an index of mechanical strength is preferably from 90 to 200%. It is preferably still from 100 to 180%. The wet thermal compression set is preferably 18% or less. It is preferably still 15% or less, most preferably 13% or less.
The lower limit of wet thermal compression set of a flexible urethane foam obtained by the method of the present invention is about 2% though it depends on the density of the foam. Further, the hardness loss in repeated compression testing of a foam is preferably 20% or less. It is preferably still 15% or less, most preferably 12% or less. The lower limit of the hardness loss in repeated compression testing of a foam obtained by the method of the present invention is about 1% though it depends on the density of the foam.
A flexible urethane foam of the present invention is produced by mixing by stirring any one of the following polyols (a) and (b) with a polyisocyanate compound in the presence of water, catalyst and surfactant. In the production of a polyol foam, a cross-linking agent and other additives may be added alone or in combinations of two or more according to the intended physical properties. In this procedure, a cross-linking agent and other additives may be added to the following polyol (a) or (b), or either one of polyisocyanate compounds or to both of them. Alternatively, they may be added to a mixer for mixing a polyisocyanate compound, water, catalyst, surfactant and the following polyol (a) or (b), or to a reaction apparatus.
(a) A polyol containing at least 30% by weight of a polyoxyalkylene polyol obtained in the above-described production method of the present invention.
(b) A polyol containing at least 10% by weight of a polymer-dispersed polyol obtained in the above-described production method of the present invention.
First, a method for producing the polymer (a) will be described. A polyol containing at least 30% by weight of a polyoxyalkylene polyol obtained in the production method of the present invention is used. The preferable content of this polyol is at least 50% by weight. It is preferably still 60% by weight. When the content of a polyoxyalkylene polyol of the present invention is less than 30% by weight, durability of the resulting urethane foam, molding property of the foam, and the like lower.
As polyols which may be used together other than the polyol obtained in the production method of the present invention, there are listed a polyoxyalkylene polyol having low monool content (corresponding to Cxe2x95x90C in the present invention) obtained by using cesium hydroxide as a catalyst described in U.S. Pat. No. 5,916,994, a polymer-dispersed polyol, a polyester polyol and the like produced by conventionally known methods. Further, polyoxyalkylene polyols having different OHV, Cxe2x95x90C, contents of an oxypropylene group, contents of an oxyethylene group, or average numbers of functional groups may be used in combinations of two or more.
The preferable molecular structure of a polyoxyalkylene polyol of the present invention is a polyol obtained by using as a polymerization initiator a compound having 3 to 4 active hydrogen groups, and the polymerization initiator, there are exemplified glycerine, trimethylolpropane, pentaerythritol and the like among the active hydrogen compounds as described above. OHV is preferably from 10 to 70 mg KOH/g. It is preferably still from 12 to 60 mg KOH/g, most preferably from 15 to 55 mg KOH/g. The content of an oxyethylene group by addition-polymerization of ethylene oxide is preferably from 5 to 30% by weight. It is preferably still from 6 to 25% by weight, most preferably from 8 to 20% by weight. When the oxyethylene group content in a polyoxyalkylene polyol is over 30% by weight, wet thermal compression set of a flexible foam tends to deteriorate. It is preferable that an oxyethylene group is introduced at the molecular end of a polyoxyalkylene polyol. It is because of this, by introduction of an oxyethylene group to the molecular end, the primary hydroxyl group ratio at the molecular end of a polyoxyalkylene polyol increases. Among polyoxyalkylene polyols of the present invention, those having a primary hydroxyl group-forming ratio of 50 mol % or more is preferable. It is preferably still 60 mol % or more, most preferably 70 mol % or more.
Next, a method for use of the polymer (b) will be described. There is used a polyol containing at least 10% by weight of a polymer-dispersed polyol obtained by the production method of the present invention. It is preferably at least 15% by weight, and preferably still at least 20% by weight. When the concentration of a polymer particle in a polymer-dispersed polyol is from about 30 to 60% by weight, the upper limit of the amount used of the polymer-dispersed polyol is preferably about 60% by weight. A further preferable upper limit is 50% by weight.
As the polyols which may be used together other than the polyol obtained in the production method of the present invention, there are listed the above-described polyoxyalkylene polyol of the present invention, a polyoxyalkylene polyol having low monool content obtained by using cesium hydroxide as a catalyst described in U.S. Pat. No. 5,916,994, a polymer-dispersed polyol obtained by using this polyol as a dispersion medium, a polymer-dispersed polyol produced by a conventionally known method, a polyester polyol and the like. Further, polyoxyalkylene polyols having different OHV, Cxe2x95x90C, contents of an oxypropylene group, contents of an oxyethylene group, or average numbers of functional groups may be used in combinations of two or more. Further, polymer-dispersed polyols having different OHVs, polymer particle concentrations, and ethylenically unsaturated monomer units forming a polymer particle may be used in combinations of two or more.
In producing a flexible urethane foam, water acting as a foaming agent, a catalyst and a surfactant are used in addition to the above-described polyol. Water functions as a foaming agent since it reacts with a polyisocyanate compound to generate a carbon dioxide gas. The amount of water used is preferably from 1 to 8 parts by weight based on 100 parts by weight of a polyol containing the above-described polyoxyalkylene polyol and polymer-dispersed polyol. It is preferably still from 2 to 7 parts by weight, most preferably from 2.5 to 6 parts by weight. Hydrofluorocarbons, hydrochlorofluorocarbons (HCFC-134a and the like), hydrocarbons (cyclopentane and the like) and the like which have been developed for the purpose of protecting the earth""s environment may be used as a foaming aid together with water. The amount of foaming aid used together with water is preferably from 1 to 30 parts by weight based on 100 parts by weight of a polyol though it depends on the density of the intended flexible foam. It is preferably still from 2 to 25 parts by weight.
As a catalyst, conventionally known compounds can be used. The amount used thereof is usually from 0.005 to 10 parts by weight based on 100 parts by weight of a polyol. It is preferably from 0.01 to 5 parts by weight. As specific examples, for example, aliphatic amines such as triethylenediamine, bis(N,N-dimethylaminoethyl ether), morpholine and the like, organotin compounds such as tin octanoate, dibutyltin dilaurate and the like are listed. These catalysts may be used alone or in combinations of two or more.
As a surfactant, conventionally known organosilicon-based surfactants can be used. The amount used thereof is from 0.1 to 4 parts by weight based on 100 parts by weight of a polyol. It is preferably from 0.2 to 3 parts by weight. As the surfactant, there can be used, for example, SRX-274C, SP-2969, SF-2961, SF-2962(tradename) manufactured by Torayxe2x80xa2Dowcorningxe2x80xa2Silicone or L-5309, L-3601, L-5307, L-3600 (trade name) manufactured by Nippon Unicar, and the like.
As other aids, there are a cross-linking agent, flame retardant, pigment and the like, and they may be added according to demands. When a cross-linking agent is used, a polyol having an OHV of 200 to 1800 mg KOH/g can be used as the cross-linking agent. For example, there can be used active hydrogen compounds like aliphatic polyhydric alcohols such as glycerine and the like, alkanolamines such as diethanolamine, triethanolamine and the like; polyoxyalkylene polyols having an OHV of 200 to 1800 mg KOH/g, and the like can be used. In addition, conventionally known cross-linking agents can be used. The amount used of a cross-linking agent is preferably from 0.5 to 10 parts by weight based on 100 parts by weight of a polyol.
It is also possible that a resin premix is previously prepared by mixing a polyoxyalkylene polyol or a polymer-dispersed polyol, water, catalyst, surfactant, and further, a cross-linking agent, flame retardant and the like according to the objects, and a foam is produced from the resulting resin premix. To this resin mix, a pigment, ultraviolet absorber, antioxidant and the like can also be added as other aids.
As the polyisocyanate, 2,4-tolylene diisocyanate (2,4-TDI), 2,6-tolylene diisocyanate (2,6-TDI), and mixtures thereof are listed. Usually, tolylene diisocyanate (TDI) is in the form of a mixture of 2,4-TDI and 2,6-TDI. The ratio by weight of isomers in tolylene diisocyanate is preferably 80:20 in terms of 2,4-TDI/2,6-TDI (called TDI-80/20). Further, a mixed polyisocyanate of TDI with polymethylenepolyphenyl isocyanate represented by the general formula (3) in Japanese Laid-Open Patent Publication (JP-A) No. Hei-11-140154 is preferable. As such a polyisocyanate compound, Cosmonate M-200 and M-300 (trade name: manufactured by Mitsui Chemical Co., Ltd.) are exemplified.
The mixing ratio of TDI to polymethylenepolyphenylpolyisocyanate in the mixed polyisocyanate compound is preferably from 50:50 to 98:2 by weight. It is preferably still from 65:35 to 95:5, most preferably from 70:30 to 90:10. There can also be used urethane modified substances obtained by reacting these polyisocyanates with a polyol having an OHV of 100 to 2000 mg KOH/g, an active hydrogen compound and the like, biuret modified substances, isocyanurate modified substances and allophanate modified substances of the polyisocyanates. The NCO index in flexible urethane form is 0.6 to 1.5, preferably 0.7 to 1.4, and more preferably 0.7 to 1.3.
As the molding method of a flexible polyurethane foam of the present invention, usually, a method in which a resin premix and a polyisocyanate are mixed and molded using a high pressure foaming apparatus, low pressure foaming apparatus and the like is preferable. When a low pressure foaming apparatus is used, two or more components can be mixed. Therefore, components can be divided into polyol-based, water-based, catalyst-based, flame retardant-based, polyisocyanate-based and the like and then mixed. It is possible that such a mixed solution is discharged from a mixing head of a foaming apparatus, formed and cured as it is, to form a flexible polyurethane foam, and processed into the intended form. Usually, the curing time is from 30 seconds to 30 minutes. A flexible polyurethane foam is produced under conditions of a mold temperature of from room temperature to 80xc2x0 C., and a curing temperature of from room temperature to 180xc2x0 C.
When used in the form of a resin premix, mixing with a polyisocyanate is conducted in a high pressure foaming apparatus or a low pressure foaming apparatus. When a compound exhibiting hydrolyzing property such as an organotin catalyst is used as a catalyst, a method is preferable in which a water component and an organotin catalyst component are separated and mixed in a mixing head of a foaming apparatus for avoiding contact with water.